Did you remove the plastic film on the screen that was there when the phone came out of the package? If not, I can see why it's not easy to clean!My 25/05/11 Sensation gets smudges on its screen very easily, and they are difficult to wipe off. It's also pretty hard to see in sunlight unless it's on maximum brightness.
Strange how I'm getting the opposite experience to other people here - jealous of you!
All I do is rub it across my man boob (only when I'm wearing a shirt!) (yes, man boobs are good for something!) and all prints are gone