Anyway I'm glad to report that after 3 days of use I like it very much.
Proper numeric keyboard with T9, which I prefer over qwerty
Not too big
MiniSD (instead of MicroSD)
Aesthetic design & good build quality
Bright screen (much brighter than the M3100)
Fast & responsive (faster than the M3100)
Broadcomm bluetooth stack
Great wifi sensitvity
Rock solid stability (so far) never needed to soft reset once yet
(Not too big) but would prefer it a bit smaller, especially width wise
White backlight makes keypad difficult to read in some situations
External loudspeaker volume a bit too low, already missed a few calls
No 3G (maybe the next version?)
No built in GPS (again maybe next version?)
Most of the other things are WM5 related so I won't go into them here
The phone I've been using for the past 2 months is an Orange SPV M3100 which has been painful experience. It regularly freezes, randomly decides not to sync, regularly needs to be hard reset after behaving well for a while & wifi performance is weak amongst other things. Maybe I was unlucky & got a duff unit.
The Asus, on the other hand, has been rock solid out of the box. Not once has it froze up on me even after installing all my favorite programs & utilities (the SPV was incompatible with a couple of programs). It's been a real pleasure using it for the past 4 days. The relatively small size coupled with the numeric keypad makes it feel like using a normal (smart) phone. It's not perfect by any means, no 3G being the most significant, but for now its 85% of the way there for me.
Here's a quick side by side comparison of the Orange SPV M3100 & Asus P525