I've used NextGEN Gallery for a long time now, and I've been happy with it. But since they got bought and it became a product of Photocrati, it's really gone downhill. I don't write many reviews, but I hope to give someone else a fighting chance.
The newest update completely broke my site. NextGEN was interfering with several other plugins including Broken Link Checker and Business Directory Plugin. It created errors in IE 10 that completely made the site unusable with that browser. I've spent hours over the past two days tracking down the problem, and finally concluded that it was NextGEN.
If they get their act together, I might be convinced to give them another try. Until then, stay away.