So far this one is OK at best. The rendering is pretty slow although there's a lot of nice foliage in the jungle map (I have a P4 2.8Ghz, 1GB RAM and a Geforce 6) I got under 60fps for 1024x768 max details with 4x FSAA. People in the game with ATI's and AMD's also said it was pretty slow for them. The maps are pretty damn small too. There's no reason for this game to be that slow other than bad optimization.
The gameplay is very average. I don't really like the feel of weapons, they feel like plastic sticks. You can't jump in this game, which may counter jumping bunnies, but restricts a lot of what would be nice cover places. Like I said, the two maps I've played are very small compared to current generation MP shooters. One is basically a ruined city with a square street block, each team beginning at opposite borders of the map.
The default keyboard mapping is kinda weird, I killed a teammate when I tried to prone; I threw a grenade at him instead. I played too much BF I guess (Z for prone). The walking speed when you're crouched is pretty slow, so so far it makes the game a camping fest, especially in the jungle map. If you get up and "run" you're likely to be seen and shot.
So far I'd rate the multiplayer below CoD, MoH, BF, Vietcong, etc. It's the poorest Vietnam shooter yet.