I've been using the YUI (Yahoo User Interface) Library for a while now and had a need for a pretty complicated table/grid and decided to give their DataTable a try. It is still in beta and probably why I ran into a few quirks and bugs I just couldn't work around. So I gave ActiveWidgets a try and have been really pleased with it so far. Seems to be nicely designed and although I also ran into a few quirks it was very easy to work around them. Definitely seems to be worth the dollars rather than spending the time getting YUI working. I fully expect YUI to work nicely down the road but I can't wait for it right now.