FWIW - the snap-on hard case for my Moment degraded it's slide-out keyboard integrity very quickly.
The little ears that reach around and do the actual snapping-on creates a shear force on the slide mechanism that's orthogonal to its elastic dimension.
IOW - place your phone in front of you, left-right is X, towards you is Y, up/down is Z.
As you slide the keyboard out, that's Y movement.
The snap-on case is stressing the hinge mechanism in the Z direction if it in any way goes just slightly around the edges.
My Moment got loose in less than 3 weeks of use of that.
Your case may be different for the Epic, but forewarned is forearmed.
PS - Sorry marctronixx - stopped at the no name calling; just saw the admonition to not post about cases here. Was more concerned about someone not damaging a new phone, jumped the gun.