I use my L950 as a daily driver with the very latest build on the Insider program, the essentials all work i.e. making and receiving calls, texting, WhatsApp etc. though sometimes you may not be able to swipe up when the call comes in, you'll need to lock the handset, then unlock it again and then you'll be able to swipe up and take the call. It doesn't do this every time, but often enough to frustrate me a little. Also sharing media such as photos via Outlook is very temperamental.
So although there are issues, my phone never crashes or spontaneously reboots, and generally it's OK, apart from some niggles as mentioned.