Again, as stated many times before gorilla glass is stratch resistant,, not stratch proof. Sprint reps are training stores on the fact that it can scratch and that spot on the screen thathas the scratch is no longer 3D capable. Not worth the risk.
EVO - LUTION 3D
IMO they are probably just trying to get you to buy the screen protector, I had an Evo 4g w/o case or screen protector since launch and never had any scratches/cracks etc. I dropped it 3 times (all three times on carpet, but nonetheless) and it was fine.