I had a great time playing the map last night. It was a ton of fun I only had the chance to play as Soldier and Demo but I've already discovered 3 or 4 ways to get on top of the reactor. Though I was working on another way I don't know if its possible. (As a trick jumper from Quake 3 I tend to find ways to jump to different spots =D)
The only parts of the map I have complaints about are the bases and the reactor top. The Blu base in particular seems easily infiltrated while Red usually doesn't have that problem (seeing as they can exit their base earlier.) I think restricting Reds to the lower floor (blocking off the sniper deck air-duct) would allow Blu players to at least leave their base before dieing horribly.
My other problem is that Soldiers and Demomen atop the reactor seem a bit too self-sufficient with all of the health and ammo available. Considering that each small health pickup gives 30% health and there are three of them, a soldier can pretty much stay up there without much fear aside from a sniper headshot, then again this problem is magnified if the sniper is Blu. Since the soldier's teammates are usually standing right next to the sniper. Limiting the health and ammo to one medium pack a piece would be ideal in my opinion. Other health kits are all large but only one requires a risk to obtain. I already learned to not go back into that box, rather I'll just retreat and go up the nearby stairs.
A neat gameplay suggestion would be to have a button in the control room where teams could open or close the reactor core. Blu would have to control the room to attack the core. Though this might be difficult considering Engineers could always just build next to either and tank their sentry.
Fun map, can't wait to see the final product.