Same as clown .. i'm using the M600...
I have to say its 1 of the most stable mode devices out there. Like all windows machines / devices, it'll need a soft reset once in a while. Other than that - its stable as hell.
I was streaming MP3s from shoutcast via wifi on TCPMP player surfing on Opera and chatting on MSN without even lagging
The upgrade bug bit me...I did put my phone up @ VR-Zone for sale... decided to keep the set unless a good price is offered. Mine's the first generation M600 (not reloaded). No issues so far.