I've finally had a chance to look at Tapestry.
Wow! That is a pretty impressive bit of work. Firstly, it has a nice demo that works straight out of the
box (although you need to run an ant script to deploy it - I'm not sure why it doesn't just ship with a
deployable WAR). Secondly, the demo has lot of stuff that I've never seen other frameworks supply (eg, the property
inspector). It gives you the impression that it really is a lot more advanced than anything else out there.
It's hard to see what Tapestry competes with. It's more than just a MVC (struts/webwork etc) framework -
I guess JavaServerFaces+MVC framework is in the same area. Having done a reasonable amount of tag library development
myself, though, I am yet to be convinced by JavaServerFaces.
If Tapestry came with a GUI development tool then it would match ASP.NET+Visual Studio quite well.
Spindle - an Eclipse plugin - is available, but it doesn't
support Tapestry v3 yet.