Yeah it still has some classic maps.
There are no more grenades unless you're a demo
Scouts have a powerful sawed-off shotgun and can do double-jumps, no more caltrops either.
Medics channel heals to players and as they do so gain an "uber charge". If they fill up their uber charge bar, they can make themselves and the person they've been channeling heals to invincible for like 10 seconds or so. You also have a "syringe gun" as your main source of attack when it does come down to defending yourself, but you're mainly just keeping everyone alive.
HWG is pretty much the same
Soldiers are pretty much the same, but they hold a LOT more rockets now. You pretty much never run out of ammo before you die
Engineers are pretty much the same, but can now build teleports as well so that you're able to cut travel time and all that.
Demos are pretty much the same with the whole normal grenades + nades you can detonate with the press of a button.
Pyro is pretty much the same
Sniper's don't have to hold down their fire button to bring out the laser sight anymore. When you press the zoom button, it shows up as a weak dot through your scope and gains strength depending on how long you're in zoom. When it reaches 100% power, your shot is the strongest.
Spies probably have the biggest change from their original. They can disguise themselves still, but they can also cloak themselves for a short time (invisible + dropping disguise to allow you to move at normal speed) to actually get behind enemy lines and sneak up on people even better. Backstab is still the main deal, but what's nice is that you also have sapper charges you can put on the items that engineers build that will cause them to explode.
I think that's about it as far as classes go. Correct me if I'm wrong though. o.o