Well, I have fairly mixed feelings but do somewhat regret it.
I was a rare case with the sleeve, with a high level of complications that continue to this day, 2.5 years later. This is combined with the fact that I was on TPN (total parenteral nutrition/IV nutrition) for months after my surgery. This was during the time when most of the weight loss normally occurs, but TPN isn't designed for weight loss at all since they're trying to get your body to overcome your complications, so I lost that loss period.
Overall, I lost and maintained a loss of 40 lbs or so out of about 100 I wanted to lose. Now I'm desperately trying to lose extra by working out daily, carefully tracking all food intake, etc., but my sleeve was made with a large bougie and doesn't give much restriction, so I am pretty much where I was before surgery, except I am restricted from binge eating at one sitting.
Do I regret it? I suppose I have to weigh the fact that my 40 lb loss has been stable and I've been able to jump off the yo-yo diet platform for years against the ongoing complications I have from my surgery. So, I have mixed feelings. Since the surgery is over now, I can't say I completely regret it. I appreciate the restriction that I do have. Would I do it over again? Probably not...