Funny... even though "3dfx is dead", my V5 still works great.
To suggest LXi purchase a NV20 instead makes no sense, since there'll be like a $400 price difference.
DX9? Wtf? Like a GeForce will be DX9 compatible, whenever DX9 actually comes out... A couple years, at least? It's still gonna be a while until DX8 is fully utilized.
MX? The V5 smokes the MX in just about every conceivable circumstance.
Driver support. Yeah, there probably won't be any new drivers. There is a current WickedGL driver for the V5. Will they make more? Probably not, but who knows?
Current 3dfx drivers are excellent. It's pretty rare that a driver is updated to support an incompatible game. An API like DX, yeah. But not a game. So, I personally am not worried about future game compatibility, until T&L becomes a reality. But haven't we been promised "X" number of games for LAST Christmas? And now there's just a few... none of which I can't run just fine on my V5.
I know you guys don't see it. But 3dfx does offer a lot in their product that other companies do not. LXi sees it, and it's really ok if he wants a V5. You don't need to talk him out of it.