I've worked for a large mattress retailer for about 8 years now (one that was ranked fairly highly in a recent Consumer Reports article), and I will tell you - be weary of any consumer reports-type articles telling you what mattress you should own. The bottom line is that backs are finicky. What works for one may not work for another. Therefore, you need to make sure you shop somewhere that has a comfort guarantee, in writing. Unfortunately, our industry is full of people with less than honest intentions. Therefore, get everything in writing. Costco, for obvious reasons is a decent place to buy a mattress, but don't expect any type of help in selecting a bed, or recomendations based on your sleeping problems.
As far as the warranties are concerned, again, our industry has some shady people in it. It's too bad, but if you take it up with the manufacturer then you'll definitely get some service. Also, I know that some people get a bad impression of a warranty because they don't understand what they cover, and why they cover what they do. A sag has to be X inches to be considered a defect. The reason for that is foams conform to your body if they are doing what they are supposed to. Seriously, if you have a mattress that's not just rock hard and has no give, if you sleep on a mattress for 6 months and there is no impression, then call the store you buy the bed from. Something is wrong. The 2 exceptions to this rule (and it makes zero sense to me why) seems to be Sleep Number Bed, and Tempurpedic. Even the other brands of the all foam beds I've sold had this issue (Sealy, Simmons, and some cheaper brands as well). I don't know why these 2 brands are like this, but they are. I have my own reservations about the Sleep Number bed, but that's more because my wife and I like to, um, cuddle, and it was difficult for us to do this on that bed. However, they are a very good product as far as durability, support, and general comfort go.
Feel free to ask me any questions, I'll try to check this thread regularly, I have a ton of knowledge about beds, and I might as well use it for good, as opposed to the evil that is trying to make a buck by slingin' springs.
Cos, just a question, what happened to make you feel that way about the retailers themselves? Again, I know that there's some - issues in our industry, but the warranties are the manufacturer's and a lot of times the retailer just processes them. I'm sure you were wronged somewhere, and that's too bad, but I'm in the mood for a story - care to share?