I haven't had a gastric bypass for weight loss but had a similar thing because they needed to take bits out for medical reasons.
So maybe my take on the side-effects is a bit biased since I have them but don't have the beneift of losing excess weight (i'm severely underweight from my gut probs)
I only eat at night when I get home - because of dumping. and it does make you need to go to the toilet RIGHT NOW so I know where all the toilets are anywhere I am. But I think the worst part of dumping is when you eat something very sugary it gets dumped and because it is very concentrated in your bowel it sucks all the water out of your body - you get really dehydrated and pass out and get short of breath and it requires a trip to ED. but if I know that's going to happen. the food has to be yummy enough to be worth a hospital trip and at a time of day when I know the hospitals usually quiet.

I know many people have had gastric bypass and think it's wonderful but I always think I would never want to inflict my symptoms on someone else. I think gastric banding is ok - once you start doing things to small bowels, some are fine but some have big problems. But the side effects could be better than being obese and all the problems that come with that.