Joost isn't brimming with fantastic content, though there are some interesting titles for sure. However, it is now on the iPhone (iTunes Link). Interestingly it works only over Wifi. While this is a nice little application, it is most important because it means that slightly more exciting applications like Hulu and Slingplayer are both possible.
This class of media broadcaster seems like a great pick for the iPod touch - since AT&T isn't letting the video stream to be played over 3G. Early reports day it is more than slightly buggy but its on the store - which is the big victory