qooxdoo

I've been working with Qooxdoo for a couple of months now and I can definitely say it's been worth the investment. It's well-rounded, pretty-well thought out, evolving nicely, has a plethora of widgets, controls and other goodies to play with, has very nice docs available, browsable API's, lots of working demos, an online playground to quickly try out your own code, a very active mailing list, and lots of other good stuff. I think on the whole that it perhaps may not quite be to the same level (YET!) as EXTJS, but it's definitely headed in the right direction and getting there. And it's VERY usable. I honestly have no idea why it isn't more widely known and used. It has everything you could possibly want except maybe a good "Gui-Builder". But I don't particularly consider that a bad thing-- except it might be nice to use one to mock up screens or something now and then. All in all, I'd have to give Qooxdoo a VERY solid 8 out of 10 rating for maturity, usability, overall documentation and support, and of course ability to make what you need out of the available parts and pieces. Two thumbs up! Kudus to Qooxdoo !!