I can't give any first hand experience, my back is fine. I can pass on the secondhand experience of clients though. About 30% of them are fusions. (I work for a workers' compensation firm.)
The surgery, for most of them, seems to be a last, last resort. Doctors don't recommend it much for young (read under 50) people. I have clients in thier 20's & 30 getting them, though. Even under best case conditions, they are going to be in some significant pain even after healing out.
They have to stop smoking to be eligible. The heal out time is a bummer, they have to wear a brace that looks like a cross between between body armor and an IMac. The meds are so addictive many of them have problems with it. Many of them have a lot of depression involved with it. One of them had complications that I won't be able to discuss for a long time, as they may lead to another case.
100% of them seem glad to have it done, but 0% of them expected it to be as rough as an experience as it truly is. Again, none of them are pain free, but they all pretty much scoff at their pain level now compared to what it was 'before'. All of them seem to have the same attitude that actually get it done, none of them wanted it, but felt like they truly had no other choice.