I started at 373 lbs. Two years later, I was down to 138. I had the expected "bounce back" regain in year 3 (unfortunately, I went over the expected "bounce back" weight of 10-20 lbs - but then, I'd lost a crap ton of weight - more than a lot of people)
as GreaterFood said, 65% loss of excess weight is average, but as with any average, there are lots of people who fall above or below that. It all depends on how compliant you are with your plan, and your motivation. I was more than ready to get rid of that weight once and for all.
I didn't originally set a goal of a normal BMI; I told my surgeon that I wanted to get to 200 lbs, which at the time seemed like a pipe dream - but I blew through that. I switched goals a couple more times, the last one being a normal BMI. I was told that was a bit unrealistic as only about 10-15% of their patients manage to get there, but I made it (and btw, that 10-15% stat is backed up by some of the research articles I read, too).
but even if I'd only made it 200 lbs, I would have been overjoyed. I looked 100% better at that weight than I did at 373, of course - my health was much better, and I could finally do all the things I wanted to do but couldn't while I was super morbidly obese.
life is absolutely terrific. I wish I had done this YEARS ago - and I would go back and have it done every year if I had to. I never dreamed I could be at this weight and I am really enjoying my life as a "normal" person again!!
excess skin - I had a ton of it, but it was easy to hide in clothes. However, I eventually had it removed because I hated looking at it. But I'll attach a picture of me from BEFORE I had plastic surgery. You'd never know by looking at the pictures that my torso, especially, looked like a Sharpei puppy, but it did. Other than the scars, I have a normal-looking body now.