I had given up on Joost because of lack of good content, and because the player doesn't work on my Mac anymore. I'm currently testing Adobe Media Player (watching CSI NY as I write) and yesterday I fooled around with Hulu. Oh and I also had a look at tv.adobe.com which interestingly has a homepage layout that is identical to Hulu.com ... some connection there?
Both hulu.com and Adobe Media Player have great interfaces, based on standard technology (Flash/Flex & Air) which works perfectly on many platforms. OK, Joost may be a bit more creative, but Hulu and the Adobe Media Player simply do the job. Streaming (even full screen) delivers a great experience, I can't wait to attach my Mac to the big screen at home. I suspect the quality will be as good as standard digital TV.
Even more important is the content. Hulu (if you can get past the IP-blocking for non-US viewers) offers a huge database of movies and TV shows I really want to see, and the latest episode of CSI N.Y. is rolling in swiftly on the Adobe platform.
I just found a lot of reasons to throw out the iDTV box and put a Mac Mini in place. No Apple TV though, because I want to get content from more then just iTunes. TV is really in for some big changes over the coming years, that much is clear.