My browser literally freezes for about five minutes every time I open a link to anything on Imageshack. My terrible terrible computer together with my mediocre internet connection just can't handle loading so many flashing ads and pop-ups. I'll go ahead and join the group of people saying "please upload somewhere else".
On the other hand, I've been using Photobucket for years and have had... well, relatively few problems with it. It's slow to load for me at first, but at least opening links to images there doesn't cripple my computer.
And then there's Tinypic, which I started using earlier this year for Craig's images. It actually seems to work out pretty well for me. I might switch over to Tinypic entirely at some point.