Know a few who have had it; some have maintained their weight, others haven't. Bypass is considered the gold standard because it generally results in the most dramatic/quick weight-loss, however, dramatic and quick loss is rarely ideal. To me, gastric bypass is way too invasive and I'd rather have all of me in tact. The fact that you have to worry about dumping and have to live off vitamins for the rest of your life is a turn off for me. I don't want to be taking pills everyday for the rest of my life due to the fact that my system has been altered in such a way that I can't absorb certain vitamins.
Even though results are usually promising with bypass, all surgeries require a lifestyle change. Knowing how to eat and the importance of moving (note, I didn't say exercise) is critical for anyone losing weight, with or without surgery.
Plenty revise to bypass, but I've also seen bypass patients revise to Lapband; it's a catch-22. If you're willing to make the needed change, any surgery will work, so will non-surgical methods.