Cowon's video ability is amazing. Looks really good - much better than Archos, or N770 at least (dont have a n800).
I have an A2 and I think it is worth having a dedicated video player for communting etc. if thats what you want to do. One of the most useful features on Cowons is zoom on the fly while you are watching video so you can see the movie even bigger (when cropping is Ok). I wanted to watch video on my 770 but sadly it doesn't compare. (love both of these machines though).