Especially if you have back pain you will notice tremendous difference in the severity of the pain just by changing your footwear. Many other musculoskeletal conditions also improve, and I notice it really affects my neck pain and head aches. Well cushioned weight distribution with good support is the thang, and now if they can merge that package with snazzy design, it will be worth the investment for any chronic pain patient.
Exactly what shoes to get is a very individual question, and I recommend you get professional advice. Most bigger cities have specialized shoe stores where they actually test your walking by filming you on a treadmill with and without specialized footwear before advising you on what shoes to buy, and they have physiotherapists working there. Well, that's the place you want to go to.
If you can't find such a place, or won't be able to get to one for a while, find the best place you can and request their help. For excellent shock absorption and support, aerobic shoes can actually be really good, though they tend to wear out quicker than other more sturdy outdoor shoes. It may be worth getting a new pair every year if it helps your pain. I used to get special shock absorbing orthotic inserts and got good help from those, but recently I tried out MBT's and they definately changed the way I walk, and help the pain a lot.
If you have herniated discs, shock absorption makes such a huge difference I would recommend you to go out and buy new shoes right away. And girls, forget about the high heels. It's just not worth it. Some beautiful sequined ballerinas with shock absorbing heel inserts will allow you to move freely (maybe even hit the dance floor?) without provoking a pain spike.