The only issue I've had with the screen on my DI is when i have it attached to my S2 SoundGate car mount. Using swype is damn near impossible and icons require using a lot more effort to get them to press, AND if you don't hit them absolutely dead in the center they won't press either. (which is fine, I shouldn't be texting while driving anyway)
I tried using the phone on carpet, blankets, tables, etc, and it worked fine. However, I tried using it on top of a soft foam insert mold (from a stethoscope box) and it had a little trouble reading button presses. Seems like this is the same problem as yours but much less severe.
But hey, as long as it continues to work in my hands, I'm happy. =D