I, for one, love it - because it enables Jlaw to hit the ground running on the backend. Everyone already knows and loves the UX. Just need to work out the optimizations like you said.
Yes, Sync for Lemmy is a battery hog in my case too. So much so that I uninstalled it a week or so ago but then installed it again since all other apps are not my cup of tea. This time I have restricted its background usage and it seems much better now.
Uhh I'm no mathematician but 8% for firefox at 8 hours and 8% at 2 hours for sync kinda tells me sync is eating your battery but again im no mathematician and I'm also extremely blazed right now.
I honestly pop into Firefox for a couple seconds and back out. I spend way more time in Sync. The Firefox bug is known to the developers I believe, but Nightly, so...
I guess the actual usage doesn't seem bad, compared to my browser with similar active times.
The warning was for frequent wake ups which makes sense with the background usage. I set it to limit background for now, at least until push notifications are implemented, as I don't think there's any reason currently to be active in the background.