I haven't really started banging on any of mine yet, but I was pleasantly surprised to log in to only one error message from an addon under my care.
The error was in Dye Station Achievement Links, had to change ZO_Dyeing to DYEING (which was originally how I thought it should have worked, but didn't).
I noticed in the source code some inconsistencies with the usage of
collectible/collectable. Might consider ironing that out
I'm excited to see what may be possible with the champion UI, collections UI, and crown store UI.