I've been using my u10 almost daily (week days that is) since getting it as a gift last November at Max 2005. I'm really pleased with it; it's small, has a great interface, and the D-click navigation is really sweet to use. All in all, a great little portable player.
The only thing I had had difficulty with was loading video onto it. I could not find any utility that would allow me to convert videos to view on the u10. Then I came across the iriverter, a nifty utility that was still in early development but that could convert videos for a bunch of iriver players, including the u10.
I though I had found 'the' tool, but my enthusiasm quickly died when the videos I had converted using the iriverter could not play on the u10. I was back to square one.
That was a few months ago, and a version back. The latest version of the iriverter (version 0.16) works very nicely with the u10. I was able to convert DVDs and a few QuickTime movies, and successfully play them on the u10. I'm still having some problem converting .wmv files, but that will probably be fixed in the next versions. I now have 3 episodes of Skyland to watch and a few EVE Online trailer I'll be able to show around.
I'm quite happy about it and can't wait for tomorrow's commute to work!
Here are a few useful links: