Mattress is pretty firm, although it does seem to be getting more comfortable with time. So far my experience has been just, meh. Don't love it, don't hate it.
We've had the same mattress for about 12 years. We were going to buy a purple mattress, but saw this as an option. My back would hurt after about 4-5 hours and then I'd wake up. It was a terrible alarm clock. Sleeping on the Tuft and Needle has been transcendent. I don't wake up with back pain, I am able to sleep more soundly and it has made me lazier. I don't want to get out of bed. The Tuft and Needle is a dangerously awesome mattress. Granted, we've only had it for a month and switched from a queen to a California King (I'm 6'6", 210), but I look forward to a few years from now to see if it is still the same.