Windows Phone 7 have come a long way in terms of responsiveness & performance. Perhaps a good benchmark of the improvements they've made to the operating system since MIX10 and certainly its debut at Mobile World Congress is the start up time. The short video below features a prototype LG Windows Phone 7 device with a recent but stilln't final build of mobile OS doing a cold boot after removing & replacing the battery. Consistent across several tests device booted in an impressive 30 seconds. What's remarkable is that as soon as the lock screen displays, it's fully initialized and ready to be used.