I played the combat-heavy part of the demo with each class. Be aware that classes are somewhat different in multiplayer and single player due to the different species and ability restrictions. For example, playing a Krogan soldier in MP is way, way, waaaay different to playing soldier Shepard in SP.
The following is based on single player:
- Vanguards, my personal 'primary' class, are more fun than ever. It's like playing as a biotic wrecking ball. Charge is still awesome, nova is fun and looks spectacular, shockwaves have been changed. Love the biotic falcon punch.
- Soldier is still completely dull. I have no idea why anyone would play it. You get to shoot stuff, shoot stuff in slo-mo and shoot stuff with different bullets. Now they cn throw grenades, but they get the most boring kind of grenades.
- Infiltrators seem largely the same. Hard to judge properly since there aren't any sniper rifles in the SP demo.
- Adepts are tons of fun. Enemies on higher difficulties don't all have extra shield/armour/barriers, so biotics are much more useful, but not as overpowered as they were in ME1. Also, cluster grenades are amazing.
- Sentinels are a bit meh. Like the OP noted, the tech armour no longer gives you an instant recharge. Instead, it gives your shields a damage reduction. On the other hand, you can detonate it whenever you like which is cool.
- Engineers, for the first time in the series, are actually fun to play. Good all-rounder class, especially now that you'll be able to choose your weapons. Drones are more useful, the little deployable turret is surprisingly badass. I'm hoping it'll can change my imported sentinel to an engineer.
Incidentally, they changed up your squadmate's abilities as well. Garrus is still a useful all-rounder, but now he can drop mines. Liara is ridiculously powerful. With the right build she can hurl biotic nastiness around almost constantly.
