Well, a premium member may get something exclusive to Premium Members..
Some ideas would be like:
A shirt from ComputerForums
A mousepad from ComputerForums
A special forum for premium members...
Or, maybe special forum permissions like the ability to change your own user title or something that members would like..
Maybe David could look into something like getting a discount with advertising on ComputerForums as well.
Another option would be if possible by David, a magazine from ComputerForums, or something along those lines..
I'm sure someone could come up with ideas..
Basically, it could be very similiar to a donation to ComputerForums, because its going towards improving and maintaining the community, but you have incentive by recieving something back as well.