Well, I haven't been at this quite as long as
DianaCox, but over 12 years is still a significant time. I don't have a backpack and don't know, or know of anyone else, carrying around gobs of vitamins in one. I do know a lot of very happy people who last weight successfully, and have kept it off without strict dieting. Not that we don't have to pay attention to what we eat, but it's a whole different way of life, and a much better one. I will gladly take a few more pills every day for that.
What the best long term studies have shown is that the rate of nutritional deficiencies with the DS is remarkably low, AND when it does happen it's almost always due to noncompliance. And that's what I've seen on message boards as well - the people who complain a few years out about their health maladies were not complaint, or got terrible advice to start with, didn't get and/or follow the necessary labs, etc. The people who do play by the DS rules do very well.
What I have also seen is that some people do well with SIPS (or whatever you want to call it) and some do poorly. Some of the ones who do poorly were misled into thinking they were getting a traditional 2 anastomosis DS, find out only later, when it's not working so well, that they got a SIPS, and are very upset/ frustrated/distraught/angry.
But you're gonna do what you're gonna do, and I hope it does work out for you, but don't be surprised when you find yourself continuing to diet to sustain whatever weight loss you achieve.