The company I work at is using it for a CMS.

Drawbacks of it seem to be large initial download (Total initial download for the CMS's files is 1.1Mb, of which almost 900Kb is JS), and some stability problems after leaving it running for a day.

As for the community "problem", in addition to pay-for support, there's a also lively forum and IRC channel.

Not too big a fan of it, imho the benefit of using extJS seems to be a large download, and dropshadow'd floaty DHTML-windows. Meh.

I use ExtJS for an application that I created. While I find it's licensing model an annoyance I have also found that, for the facilities it provides, it's unmatched in terms of quality and breadth of offering. I know there are a number of other potential alternatives out there but I have found that I like the way the components look, it's strong in the cross browser support arena and believe theres a coherence to the API that simplifies learning how to use it too.

My concern is that it does not really foster a community around it so with the odd licensing model and without the community itself it can slow behind other alternatives.

I can't argue with that but I suppose the way that they are looking at this is that, as it's least partially a commercial venture, there are people being paid to keep it concurrent. Only time will tell whether this is how it actual works out however.

I don't understand where you are coming from.

TANSTAAFL!

We bought a licence and use it to write our product. It works great!

And "community"? There's a huge, active and enthusiastic community!

The problem is not the license per se, but the bait-and-switch they did. http://www.jroller.com/sjivan/date/20080425

I'm using it with AIR to create client-side apps.

I've enjoyed it so far, it seems very elegant, but can be a bit tricky to learn.