Hi, I have a couple suggestions and I should probably introduce myself a bit.
I've been playing the preb3 and b3 versions that I was given by tarmo in PUGs and scrims, I do play competitively and while my team is not yet in a league (all the leagues are either mid season or inbetween) we do actively scrim. Tarmo, if you're wondering who I am, I'm Jesus_ in IRC on Gamesurge (tf2.pug and tf2.pug.na)
My biggest suggestion as I play on a less than stellar rig, is a lot more optimization! I lag a lot on this map, I will be in the 10-15 fps range on mid and 2nd often, while on a much larger map (like cp_badlands) I will have consistent 30+ fps.
Now onto the general detail suggestions of the map's gameplay and aesthetics.
I'll start with middle point as it's the focal point of all 5 CP maps.
My biggest gripe with mid is that it's far too cramped, it lacks the feel of a middle point you get from maps like freight, granary or badlands, the point really only has one definite entrance and it's really not too friendly to the heavy classes. While it is very intense, it generally only has one viable strategy for the main battle. Secondly, the underside of it has far too few uses, while a scout can use it for a flank, the heavier classes barely have any space to try and spam from (e.g. a demoman spamming some pipes or stickies from valley in badlands.) it really just leaves that space as a little too situational. Basically it boils down to opening up mid, allowing more room to roam and fight for.
Now onto second point, this is by far the best point on the map. It really is a very good point to both attack and defend. There really aren't any suggestions I can think of for it other than a minor bug fix on b3. I'm not sure if TMP told Tarmo already but if someone is coming out of forward spawn the door clips through the ground in the room above and blocks entry a bit.
Final point, this is a good point as well, only things I dislike about it are that the entrances for the attacking team hardly allow for sneaking captures since they're all very visible by the defending team.
That's all I have, it's a fun map to scrim on but if a few of these things were fixed up it'd be even better.

Great work!