Yes, I would definitely use premium fuel in any car that I own.
I think that part of the fact that our cars run faster with premium might be psychological. However, I do not look at it in such a manner that a high compression engine would run better on premium, I look at in a manner such that the car runs like it should on premium. If premium is not used, you will see a decrease in performance and gas mileage because the car will be retarding the timing to prevent knocking.
In conclusion, premium may not necessarily give a boost in gas mileage, but I would use it anyway. At least in the US, the price difference is not that significant in the scope of how much it costs to keep a car running anyway.
As a side, small airplanes require 100 octane fuel that typically costs around $2.50 a gallon in the US. In the UK this fuel can run over $6 a gallon!
[Edited by Ali Al-Chalabi on 03-04-2001 at 02:18 AM]