One word for 40GB SKU owners: Supersize.
After upgrading a 60GB drive to 320GB and then returning to a 60GB refurb, I can't keep anything on that system but game installs and PSN titles.
The 320GB drive I immediately swapped out in a 40GB SKU actually started getting cramped after using it to store a fair amount of video, plus a library of demos, PSN titles, game installs, music, etc. before swapping it out for a 500GB drive.
500GB drives run about $85 currently. 320GB drives can be bought for about the price of a $60 BD game if you shop.