While I generally like the idea of Joost in general, I have a couple problems with it. My home setup has a Mac Mini connected directly to a 42 inch Vizio LCD TV.
First, I love that Joost works so well with the Front Row remote control. Hitting MENU brings up the main Joost menu and the control buttons easily allow me to access all of the channels and the sub content of each channel. They have done such a great job with this that I wouldn't change a thing.
The picture quality on my tv is heavily compressed though. Some of the content is full screen and other is standard def and has black bars on the right and left. If they could increase the video quality I bet more people would be interested.
My main complaint happened today as my four year old daughter was watching original Saturday morning cartoons of Casper the Friendly Ghost. There are commercials that pop up at various times and the first one was for Kraft Easy Mac - this spot played about 3 times without showing any other spots. Then came a preview for Hostel 3 (or 2 - so hard to tell). The commercial is dark and scary and not at all suitable for a four year old. I'm pretty sure you'd never see an ad like that on Cartoon Network or Nick Jr. - They really need to work on placing ads based on their demo.