hunger/appetite usually come back sometime during the first year after surgery (and a minority of patients never lose it at all). After that, things get more challenging. It's hard work - but it does "work" as long as you're committed and stick with your program.
during year 3, most people experience a 10-20 lb regain as your body settles in to its new set point. Of course, some people can gain much more than that if they aren't careful.
basically, the surgery keeps you from eating a lot AT ONE SITTING. I'm over seven years out, and I can't eat nearly as much at one sitting as I could prior to surgery. As an example, before surgery, I could easily eat half a large pizza. Now, I can physically only eat 1-2 pieces. Again, at one sitting.
the major problem is grazing. If I eat 1-2 pieces of pizza at 6:00 pm, and another piece at 7:30 pm. and another piece or two at 10:00 pm - ta da! I've eaten half a large pizza. So you really have to watch that if you want to maintain your loss.
like others have said, though, it gives you a huge reset. I lost over 200 lbs, which I could have never done on my own. But after that loss, it's on you.