They're responsive, intelligent, and have great pathfinding capabilities. Customization of your Gear is easy and painless. It's not quite as sensible as critical points or drop ship weight limits, but it works. Several weapons are pretty much Instant Death Blows if they hit, and since sniping is a lot of the game, you'll see quite a bit of it. Unless you're playing on a server with a ridiculously low Threat level, prepare to die quite a bit - and to conquer that learning curve quickly.
Artillery sounds great, the clank of bullets is there, and explosions are dead on.
The cut scene and in-game sounds are good, and the communication between you and your squadmates is clear, concise, and believable. The voice acting isn't quite Blizzard quality, but it's better than most and doesn't distract. I enjoyed it a lot - if I had been met with Kid Rock when I started the game I would been a bit worried. I wasn't complaining. As far as bugs, the only one I really noticed was some weirdness with the Savage 4 - during the menu screens, areas of the menu would follow the cursor around, dragging texture areas behind them.