Update on my 1020:
1. Battery usage has gotten worse, or maybe I haven't been stuck in the house so been off Wi-Fi more often but still drastically worse than on 8.1. Even on Wi-Fi and hardly using my phone I get about 8-9 hours where I'd get at least 24 hours before. Heavy use on 8.1 would get me from about 8am to 11pm before battery saver would kick in. Yesterday on W10M I got 6 hours while at home and this morning I stepped out and my phone shut off after 3 hours. Went through all the background tasks and don't see anything that I didn't have set in 8.1.
2. SMS is still slow to interact with, take a while for conversation list to come up then clicking into a conversation again takes a while to show the conversation. Sending a text takes quite a while to actually send after typing and the typing itself is laggy compared to other areas of the OS. Additionally, I get no notification alerts for SMS received although the integrated Skype does notify. I checked Messaging background task and it is running.
3. Like others launching any mapping apps just fails.
Overall I like the look and direction of WM10, mail and calendar are much improved. However, I can't test if I can only get 3-6 hours of battery when not using the phone, while using the phone the battery drain is ridiculous. Since others with battery issues have tried soft and hard resets with no success I'll have to revert to 8.1 and perhaps test the next build if these battery issues are addressed.
BTW, I updated last Friday so I've given the OS plenty of time to "settle down" with what it has to do after an upgrade.