I own a Fujitsu/Siemens LIFEBOOK T-series for about 3 months.
LIFEBOOK

My first choice was also ASUS bacause of the lower price but the LIFEBOOK's not much more and I've good experiences with Fujitsu.

I like it very much and it's very robust.
Sound is ok and battery lasts for ~2h playing (~3h programming).
GFX is fast but has no shader-support.
Tablet only accessable by pen (not by finger) but thats not a problem for me.
The screen is very good and has a wide angle of view.


Most benefit of a tablet pc for me:
- designing games concepts for touch-screen-systems (this is the future of mobile gaming!)
- texturing/painting is very easy (->ArtRage)