We just spent some quality time with the MIX10 build of Windows Phone 7 Series running on the same prototype hardware sourced from Garmin-Asus that we saw at MWC -- and apart from a few Murphy's Law-style demo hiccups, we loved what we saw. One thing that immediately caught our attention was the fact that lists of items "compress" slightly once you've reached their end -- something we hadn't noticed before. In general, it's pretty impressive how much attention Microsoft is paying to the finer aesthetic points of the platform, from the slight "tilts" of items that you've pressed to the 3D effects you encounter as you flip through photos. Another thing we've confirmed here is that the test units do have accelerometers, refuting an earlier rumor that had been spreading out in Barcelona -- we know this because the display auto-rotated while viewing a photo. Check out the full video -- along with a shot of the phone resting alongside its Zune HD cousin -- after the break.