I managed to play a couple games before work today.
The E3 videos gave the impression that it was a cross between MW2 and BFBC2 and that's exactly what it is and I quite like it. It's fast paced like MW2 and although it is fairly easy to get kills, it's far easier to get kills with headshots so you will need some skill to get to the top of the score boards. (to put in perspective, you'll need more skill to do well than you would in MW1 or 2)
The health does regen but not in 3 seconds as mentioned above, it's more like 10 which I think is long enough that you won't regen in the middle of a fire fight with an enemy but still short enough that you'll be back to full health for the next guy.
It's nice to see that the beta has been held so far in advance that there is actually plenty of time to address the many issues the game has. If they actually listen to everything being brought up, it may just be quite a game. Nothing spectacular or innovative, but a nice run and gun fps.