I think the cart does move back a little too fast, since a simple airblast can push away heavy classes enough to make them unable to catch up to the cart. You really need a scout or something to catch the cart after a certain point.
If you DO decide to remove the capture point at the top, I'm not sure how you would explain to people that LOSING occurs when the bomb reaches the bottom of the pit. I was REALLY confused when it happened to the enemy team.
Also, someone mentioned that if you want the end to be epic, make it so the winner's cart shoots to the top and makes an explosion...Uh, you could use a custom payload that had a rocket engine attached to the back =P
Overall I liked the first and last level the best. The 2nd part ended in like the middle of the map so it wasn't too hard to push after a certain point.
When we played today, the first stage was by far the best stage. The second stage became a steamroll, because the track ends in neutral territory. Neither team is able to build up defenses around the cap points, so the first team to push into the middle area usually wins easily.
The third section was interesting, but it didn't totally work. Is there a way to make the cart roll back faster near the cap point, and slower near the back of the track? That could improve it.
First: Thanks for the feedback! Just what I need to get motivated

(been working on my other maps a lot lately...)
Rant about my stages so far:
Stage 1: I'm quite happy with this stage, it plays fast and hectic, and doesn't involve direct spawncamping to win. It has a interesting start and easy layout.
Stage 2: Probably the weakest part at the moment. The goal with this stage was to bring fighting away from the spawns and make a deathmatchy arena in the middle... while that succeeded, it's not very fun. The side building on the far end are not used as much, it's easy to get behind the enemy and harass them by spawn. As you point out it feels hopeless to win once the enemy has seized control of the middle.
I might redo this one from scratch if I can come up with a good idea.
Stage 3: Could use tweaking, but I'm sure it will work in the end!
Needs some restructuring at the top of the tracks... I want the last stage to be a struggle, but still give the players a panic attack when the carts go downhill. I'm thinking this might need different strategies than 'normal' plr maps, it's going to be fun to see what ideas players develop.
The playtime on this stage has been short so far, and there are many unexplored areas still, like the highest ledge for demoman/soldiers on the middle building. Control that and you can easily decimate the enemy and force their cart down.
General: The rounds go by pretty fast, which I think is a good idea. But it might get repetative if it's too much of a rush. I hope that once I start detailing I can bring the stages together and make it feel like progress is being made upon stage completion.
But hey, when the map is named Panic, fast gameplay is a
requirement
edit: ohyeah, and I need to check lighting on everything again, some people still had problems identifying team colors (NOT GOOD!)