1. Go stay at a Radisson hotel before investing in a Select Comfort. They have them all over and you can try it out. It's an acquired taste, shall we say.
That said, it's wonderful in certain circumstances (wish to heck I'd had one during a period when i was moving around a bit, because I could manage everything in cars except for mattresses so had to rent trucks occasionally).
2. Select Comfort (queen/king) is two air bladders surrounded by semi-rigid foam (pool-noodle type stuff). If you're spooners, may not be the best, but if you contain yourselves to one side of the bed, you're fine. Tends to have some hammocking when the bed is made unless you plump up the air every morning.
3. Tempur pedic and imitators are heavy and warm. My partner and I got one in May (faux from Costco...good return policy and cheaper than Tempur pedic) because we could get it up the stairs

. Not too hot for us, a little sinky-into (you feel like you're swimming in it...I'm 6'0 240 and Brian is 6'2 280, so we're big bears). I don't think either of us are too in love with it, but given the choice between a pricy Select Comfort, a no-brand air mattress (faux Select Comfort), a pricy Tempur Pedic or a no-brand foam from Costco, I think we made the best decision for a 1920's colonial 2 story house.
4. Remember that all mattresses are basically the same...if the number of coils and the configuration (individually pocketed/Beautyrest or linked/Perfect Sleeper-Posturepedic) are the same...you're looking at the same mattress. That is, if you're seeing a 720 coil Serta at Costco, Macy's and Sears...it's the same mattress and the only differences are the cover. Also, a tight-top (i.e. non pillow-top) will probably show less depressions and allow more flexibility (featherbed, ...) with subsequent things. This also helps with private labeled mattresses...a 750 coil queen size probably comes out of one factory no matter the brand, a 768 coil queen probably comes from a different factory.