I've read a few times (and can recommend) Bruce Tate's Beyond Java (though that doesn't have a lot about UIs in it) and I'm always interested to hear views on where UI programming is going.

Another Bruce (Eckel) has written here about similar things, but whereas Beyond Java seems to have gone overboard for Ruby on Rails, this chap has nailed his colours to the Flash mast. It's an interesting article, and well worth a read, but I can't agree with the conclusions.

Eckel says Flex is free - well, so is the .NET framework if you want to do without an IDE. I don't think anyone really wants to go back to those days, which is one reason I'm also sceptical about RoR.

I had a look at the demo for Flex Builder - it's a plugin for Eclipse, which is my favourite IDE. But I'm not sure that Adobe are a good bet. They are proprietary and predatory in pricing, and I don't think it's worth £500 to take a punt on yet another scripting language. In any case, most Flash sites I've seen look good but are terrible to drive.

I stand by my view that the browser is not a stable or controllable enough platform for business UIs. Doesn't stop our building them if that's what clients want, but it's not the best solution. I predict a comeback for the thick client with an HTTP/XML back end.