Were there any other changes that might make one of these a bigger headache to get parts for than an older (S2) Elise ?
So, are the drivetrain and chassis the same ?
would things like the BOE hinge still work, etc.....
The best way I've found to determine these sorts of differences is to go to Deroure, look at a parts list, and see if they had different parts for different years. For example, if you want to see if the radiator was updated, see if it has a different part number. With any car, there will be subtle changes that go unannounced.
Less specifically, the biggest headache you'll find is just fewer used parts due to fewer used cars in the US. I can find secondhand parts for just about anything on my '05, but you'll have a much thinner market to pick from. New parts, though, all come from England anyways, so you may actually have less trouble.