We love our Select Comfort. It's really nice to have separate settings, as with my bad back, I like having my side much firmer than DH.
I actually had a smaller one when I lived on my own, and I really had a tough time when I moved in with DH and he had a regular mattress. I didn't sleep as well, and my back always hurt when I got up. I talked him in to getting a new one that fit the two of us better, and we're both really glad we got it.
Try the Select Comfort for 30 days, and if you don't like it, you can give it back and get a full refund. Or at least that's what they say anyway. Having owned two, I've never wanted to give it back.