Played this in the IMP yesterday (I think?). Really solid map, everyone seemed to like it and it was surprisingly easy to memorize the layout. I really love the the highground with the staircase at B, made for a lot of fun and interesting gameplay.
The only real problems I had were around last. I feel like last itself is too small - and I'm assuming your intent is for last to just act like a hold to stop the cart going through the choke, and when it does get through, for the game to be won easily by BLU - however, even though this is the idea behind most PL chokes, there's still plenty of breathing room for fighting in final points like Badwater's, Upward's, Barnblitz's, etc. It feels a bit too confined to the chokes to me, and if you sneak in as Spy this becomes even more clear. The fighting tends to be restricted to the chokes moreso than in other maps (or maybe the chokes separate the areas too much? Not sure). I feel like pushing RED's spawn further from the hatch and stretching the area out could help, and could also probably help make the flank round to the area facing the main choke feel less needlessly big. Despite this, I think last feels really cool just like the other areas in the map.
Other issues I had were that, when pushing last, a Sniper can watch the path from your spawn exit through the geometry at C. If you want I can take some screenshots to demonstrate what I mean. It also feels like defenders can come from all angles in the area before the valley before last, but I expect there's not much you could do about that and it's just the way the map's designed.
Good luck with this map, it's really fun.