I was a huge fan before Photocrati bought it and re-wrote the core. Now the performance drags down all pages. Even pages that do not have photos, galleries or NextGen widgets show really poor performance.
My client's web host has had to shut down our account for over use of shared resources. When we ran performance analyzer, NextGen libraries accounted for more than 55% of the resource usage on the homepage, where we weren't using anything NextGen.
Now that I've spent money to buy the Pro Version, I'm regretting it. I'm now searching for a really good replacement. Something that works like the original NextGen used to, before all the Photocrati tinkering and excuses.