I just "finished" upgrading... Did it in exactly an hour.... But I was being VERY cautious after losing my language files a couple of upgrades ago. :-)
Only one issue with my stuff:
ERROR: unable to write to $compile_dir
I changed the directory to 777 and it went away --- until I logged in. Then I saw two CUSTOM ISLANDS displaying the error. So I logged off, closed my browser and logged in again. That fixed it.
So far, so good....
YES, PROBABLY THE BEST/EASIEST UPGRADE THAT WE'VE EVER HAD.