I installed Dev Beta 3 with much hassle as Beta 2 would give me constant "cannot connect to Watch" errors. After trying for two days, I woke up the following morning and it's installed.
I was one of the folks with a 2-3 hour battery life on Beta 2 and I am ecstatic to report that I am back to 14-18 hours on my Gen 1 Watch. Other than the icons missing (as stated above) and the many copies of the same Watch in the Health app (some pre-dating the watchOS 4 Betas), I have no problems to report thus far. My Watch is still sluggish from time to time, and perhaps a little moreso with watchOS 4 than previous, but I kind of expect that considering I bought my Watch a week before watchOS 2 was released.