My (long) analysis of the unlocks I've worked with so far, in order of how much I like them.
EDIT: Added in some more weapons after trying them out.
Disciplinary Action - I doubt I'll ever change my Soldier melee again. Seriously, as a main Medic player, one thing I pride myself on being able to do reasonably well is to keep everyone healed in large groups. With this new riding crop, I can do the same as Soldier, playing support and keeping everyone speed-boosted during a push. If you time things right, you can also chain the speed boosts on yourself off of Engineers and Snipers and the like to move yourself forward at almost Scout speeds. The damage reduction also doesn't seem to be a big deal considering how many Spies I've killed with random crits trying to give them a speed boost.
Quick Fix - Probably the most creative and game-changing weapon they've introduced, and it's just about perfectly balanced. It discourages pocketing, its uber-heal lets you cap points while "ubercharged", and its insane base heal rate means more of those uber-heals to go around, and they're almost as powerful as a straight invuln in most scenarios. Also, I love being able to latch onto a Scout and move up with them to the front lines.
The two biggest problems with it are that (a) it needs a visual cue to tell the patient when they're being uber-healed, and (b) not many people now how to work with a Quick Fix Medic effectively yet. A Quick Fix Medic has no incentive to favor the heavier classes over others most of the time, and they aren't taken out of their healing job as often for uber pushes.
I still use the main Medigun most, but I'm really loving how they changed the Medic's play style so much with this new healgun. Too many games result in just a back-and-forth of uber-building and uber-pushing. The Quick Fix makes healing the Medic's main concern, and with skilled players, the overheal issue isn't as big of a pain as it seems like it would be.
Liberty Launcher - I think I may have to agree with a lot of people and say that maybe something should be tweaked on this rocket launcher to balance it against the original, because as is, it's kind of too easy to get really good splash kills. I love playing with it - I'm amazed at how much of a different 40% extra rocket speed makes for my aiming - but I can't help but think I shouldn't be doing quite as well with it as I should. It's not ridiculously overpowered, but the one less rocket magazine isn't much of a downside for such an increase in accuracy. I still love it, though.
Tomislav - Attention everyone complaining that it's overpowered: Cry some more. It's powerful, yes, but not overly so. The regular Minigun still wins at least half the time. All the calculations I've seen to "prove" that it has more "effective DPS" than Sascha revolve around both Heavies beginning to spin up at the same time, which almost never happens because any skilled Heavy knows to never pop around corners or from behind cover without pre-spinning.
The only situation the Tomislav seems to always win against Sascha is in ambush scenarios, but the bulk of a Heavy's play time is either on the front lines (where the enemy already knows he's there) or point defense (where the enemy already knows he most likely will be). The silent rev isn't nearly as ninja as everyone seems to think, either, considering the gun has the loudest, manliest bullet-chugging muzzle belches in the game.
I will be very disappointed if Valve gives in and nerfs this gun and makes it all but useless in most game scenarios, like they did with poor Natascha.
Reserve Shooter - This is actually really hard to use effectively, but I think it's going to be my standard Soldier secondary from now on. First, the ever so slightly faster weapon switch speed makes a difference, and I like that it promotes more shotgun use from the Soldier instead of constant rocket spam (this has been bugging me since, oh, the second damn stat-backpack came out). Second, even though it's hard to get the mini-crits, and they're not that much of a damage boost anyway, when you do get a kill with them, it feels so satisfying, especially with that slamming-a-car-door kablam sound it makes when you fire.
Overdose - This is a very subtle weapon, but the speed boost it gives you with a full uber is definitely noticeable if you're near a Medic who doesn't have one. I gave up on the Blutsauger a while ago and have been hoping for a decent alternative to the Syringe Gun, which I barely use for anything other than killing Spies slightly out of saw reach, and this fits perfectly for a player like me who thinks battle Medic-ing is sacrilegious.
Soda Popper - I'm not a very good Scout in the first place, and this make the class even harder for me to use properly, especially considering it's a slightly more complex Force-a-Nature, a gun I literally never used after the first two days I got it. I actually traded mine for the Overdose because I couldn't get the hang of it (I'll find another one eventually anyway). It's not that I think it's bad, just complicated and difficult to use. Mini-crits aren't really as powerful as they feel like they should be, either. I can definitely see how this could be great in the hands of a skilled Scout, though.
Solemn Vow - I actually haven't used this yet, but since it's literally a straight upgrade to the Bonesaw, I kind of don't have to. Why didn't Valve just give the enemies' health peek to the Bonesaw and make this an optional reskin like the Iron Curtain?
Shahanshah - It's a Sniper Equalizer that doesn't piss off Medics. Most people seem to think it's pointless, but I can definitely see how it's useful for a Sniper who just got meat-shot by a Scout while scoped and doesn't have time to pull a Jarate-Bushwacka combo on him before the Scout finishes him off.
Family Business - Since it's really not that different from the base shotgun, it really doesn't have that many drawbacks, but it just seems a little too simplistic. Some people want it to have a faster rate of fire, but that would basically negate the lower damage without careful number balancing. I wouldn't mind a faster weapon switch, maybe a 15% increase like the Reserve Shooter, because the only times a Heavy uses his shotgun when he doesn't have or doesn't want to waste ammo for his Minigun and switching between them is painfully slow. This is also basically useless with the Tomislav, which doesn't use ammo quickly and doesn't have a slow spinup.
Big Earner - This is a beast if you are good at getting backstabs. I am not.
Ali Baba's Wee Booties - It's obviously only useful in a Demoknight loadout, which I only tried for the first time outside DeGroot Keep yesterday, and, for what it's designed for, it's a real powerhouse. I could just never justify trading out all my explosives for a badass berserker ability (though you could still use the Caber, like Joodude's post above that made me laugh my ass off).
Persian Persuader - Another Demoknight weapon that I would never use even if I hadn't already traded it away, though the nearly-infinite access to charges is absolutely bananas. If they ever make TF3, Valve should just go ahead and make the Demoknight his own class, if only so that future unlocks for the Demolitions Man will have actual demolitions in them.
Enforcer - Spy is my least played class, and when I do play Spy, the Revolver is my least used weapon. I've actually stuck to L'Etranger for a while just for refilling my cloak, which is my Bee Eff Eff as Spy, and that's the exact reason I don't care for this gun. The damage increase is cool, but half a second is an eternity when you're trying to cloak away from a firefight. It might be awesome with the Dead Ringer, but I despise the Dead Ringer and resent attempts to get me to use it. Still, it is nice to see the Spy get his very complicated game mechanics tweaked so that straight up gun-fighting is a more viable option.
I still want to get the Winger (I know there's a lot of hate going on about it, but I've never been a fan of the Scout's beverages and I'd like to actually be able to pop off a few powerful shots with a secondary). The Bazaar Bargain would be utterly worthless in my can't-aim-for-shit hands.
