1. You won't be able to store many games with 80 gigs.
2. depending on the speed of the drive, the load times might be terrible.
that's about it.
from your other post, you'll also be using it for the OS (16-20 gigs) and also whatever other applications you might want on it... Assassins creed 3 is 17 gigs, BF3 is 10-20 gigs (depending on DLC and whether you got retail or digital edition) so that's pretty much most of your space right there. just for 2 games and the OS.