[url=http://jkontherun.blogs.com/jkontherun/2006/07/excellent_head_.html]jkOnTheRun[/url] posted a link today to [url=http://meansquare.info/UXReview/vsOQO2.html]a great OQO versus Sony UX Article[/url].
The article is very thorough and goes through everything from size to outputs all the way to which fits in your pants better. (the pants part even includes a picture to demonstrate which looks better in your pocket)
If you are trying to decide between each of these systems or just want to get an idea about each one, this is the best article you could possibly ever find on the subject.