We used to have waterbeds (after a back injury I had), and we kept buying up to better ones. Eventually the cats decided they didn't like them, so we ended up with a Serta or something. Being a king-sized bed, it tended to "sink in" in the center when the 2 of us slept together. I thought it was a problem with that mattress itself. So in 2006 I started shopping for beds. I shoppped the same stores, and I'd go on good days, and bad days. I always came back to the same bed, a Stearns & Foster Verandas 160th Anniversary Edition pillow-top. Got it home and cried. Although I had lain on it for @ 30 min each time I shopped, I couldn't spend a whole night on it. They wouldn't take it back until I'd slept on it at least 30 nights! So I bought a memory foam topper from Bed Bath & Beyond. Can't remember the name, but it was the expensive ones. 2 in thick, I think. It helped, but the bed still "sank" in the middle when we cuddled at night.
Last year I had to get another bed (for a different house), and I had thought a Sleep Number bed would be great. Can't remember what kinda I bought since I'm not at that house now, I can't check. It wasn't the TOP one, but the next one under it. Again, I researched and tried them out for months (I was a 45 at the store). Once I got it, it didn't feel quite the same, and they said it just needed to be broken in. The customer service was great. They sent me an additional foam insert to but inside it, and extended my 30 days to return it for a full refund warranty another 30 days. Well, it seemed to help a while, and then it didn't. I bought the 3" toppper this time, but I seemed to sink in (not the center, thankfully!), and it was hard to turn over, etc. I finally bought another 2" topper like on our other bed (the guest room now has the 3" one), and I generally sleep much better now. Except for when I don't.
So what I'm saying is, if you are sensitive, no matter what kind of bed you get, you'll probably have good nights and bad. Just make sure you know what your return policy is from one store to another. One store would let me exchange only but no refund (of the most expensive item in the store!!!) of the sleep #, so I bought it at the sleep # store and ended up with a 60-day complete refund warranty. I'm never sure how the beds will feel when I go to bed, so I just thank God every night if it feels good.
I hope you have less problems with your bed that I've had!