I use the MH100, the younger and less capable version of the MW600. The sound reproduction is insanely good (in comparison to the shitty motorola headset I got with my l9 some years back) and the range is quite good. You can roam around freely, heck you can even jump on ur bed like a maniac but it won't drop a call or skip. Connection speed is instaneous.
The negatives-
- everyone mistakes it for an mp3 player. Its just a bit too large. Sony Ericsson have made clamshells which when folded up are the size of this thing. You can clip it to your breast pocket or tshirt sleeve without looking bad though.
- The volume rocker is a pain in the arse. It wakes up the screen at the slightest of touchs but trying to set the volume will wear ur thumb out.
- The inbuilt Radio. The MW600 is said to have an inbuilt radio so I don't know if I'm fully accurate here. On my Mh100, the inbuilt radio only works on my Aino, not N79, N95 or other new Sony ericssons like T705.
- On compatibility front. It worked with everything I tried it with. though the keys were a bit weird. Play button doesn't start the music on my N79, it launchs the Music Player application. On iphones (as of ios3), next and previous don't work, You have to voice command 'next' and 'previous' as a work around.
You might want to try the MW600 out before buying it though. Hope I've been helpfull....