Upgraded L640XL (LTE DUAL SIM) to W10 mobile to 10586.36 through 10586.29. Performance is good, though not without few problems.
The most noticeable thing is UI which was somewhat childish on WP8.1. Now it looks more polished, mature and evolved. Of course, it isn't consistent throughout the OS and apps/games seem not to be well optimized for 5.7" screen as it's in WP 8.1.
The biggest problem is that apps, especially games on SD card don't work smoothly. Observed that games like Asphalt 8 Airborne, Jet Pack Joyride, even Temple Run 1 & 2 etc. stutter while stored in SD card memory and work smoothly while in Phone's internal memory.
(Has Subway Surfers been withdrawn from store?)
Don't know what's happened to TOUCH SENSITIVITY setting. It's not seen in SETTING>EXTRA>TOUCH.
Is it possible to change EDGE>SETTING>READING VIEW FONT SIZE? In my case it's not happening. (It can be done by changing SETTING>EASE OF ACCESS>MORE OPTIONS>TEXT SCALING.)
Speaking about Camera, photo processing is still slow. Wonder why Rich Capture mode doesn't work exactly as in WP 8.1. Lenses were not visible first even after complete installation & update of apps. After hard reset, the problem resolved.
Otherwise performance is really very good. Can be termed as snappy for most of the times.
One consistent problem which has been frequently occurring is that office apps ask sometimes for Office 365 subscription and the apps require to be uninstalled & reinstalled. It's weird.
When will MS make full features of Groove music & Films &TV available for India?
Lastly, battery life is a somewhat lesser. Though not worrisome.