For me, this is how it went:
Day 1: Complete hell. It took forever for my SD card to be recognized and I thought I had lost all of my data. I randomly looked at my phone to see what the time was and I suddenly realized that all of my apps came back.
Week 1: So far so good. The phone is kinda micro-jittery, but between the much improved Xbox Music, the actionable notifications, and the much improved settings menu, I actually liked it more than WP8.1.
Week 2: Things have slowed down a lot and the phone began crashing on me a few times per day. Nothing too bad, as I am an enthusiast and can take my phone crashing.
Week 3: Things are bad. My phone restarts at least 10 times per day and Twitter needs to be reinstalled every 4 hours.
Week 3.5: This was the straw that broke the camel's back. My SD card stopped working. I kept restarting the phone and nothing happened. No matter what I did, it said the SD card was broken. I had no choice but to flash it back to 8.1. Everything worked out fine and the SD card works again.
TL;DR It's not ready for day-to-day use.