As a frequent traveler...
I see limited appeal in bypassing the front desk. If I go to the desk, I can ask if there is a room upgrade available that wasn't already given to me, talk to a person about hotel amenities if I haven't been there before, etc. I'm sure there will be times when I will enjoy being able to just get to my room and not interact with someone (one night layovers in hotels near airports come to mind), but generally I prefer interacting with the front desk, even if that results in me waiting in line to check in.
On the other hand, I like the idea of not having to carry an extra card in my wallet three days out of the week. Being able to open the door using my SPG app on my phone will be nice, provided I can sync it to allow access to others when I'm traveling with friends or family.