If you have the extended 4-5 hour battery, I would love to know how that works!
Jenn at pocketables.net has had a number of detailed partial reviews as she is waiting for the extended battery to give a true review on the D4. She did do a 14 minute video showing how well Vista ran on it with 10 web sites opened at once, etc. The Sharp D4 handled Vista with no problems.
It is not perfect but to me it is finally one that I could live with. More UMPC companies should build an improve on this design. It is very unique as it has both the slider and the clamshell form factor.