Hold on here...

The driver only needs to be DL'ed once right?
If there are updates you may need to patch or reinstall but am I correct that once you DL the Ageia driver for one game, you don't have to do it for others?

Because if the above is true, then ALL arguements against Physx for it's driver size are moot! I mean a 20MB download may not be right for your target market (casual games or dial up users) but I think the majority of gamers have no problem doing so if you make it easy for them to find it.

Seriously, if this driver is once per version and not once per game, there is NO reason not to vote for physx.