Extra RAM is never a bad thing, it just doesn't do a heck of a lot for you with that card (more RAM on older cards only allows you to maintain some level of performance at really high resolutions but doesn't add much of a boost in performance at lower/standard resolutions).
I have an MSI gf3 Ti 200 with 128 meg of ram.
It was sold as having 128 and it came with 128.
The extra memory will help with future games. That ram will hold textures for games. Right now I think that games are written to keep the textures inside of 64 meg cards. as 128 gets more popular I think textures will become bigger.
PS this also reduces the need for AGP 4X or 8X with 128 you won't need system ram for holding textures.
FSAA also uses up memory.
I got 128 because at the time it was 10 bucks more then the 64 meg version.