It seems lately like K9 is very slow in all things. Any feedback?
Define “slow”? I haven’t noticed anything slow at all … it polls/pushes when it’s supposed to, when I manually refresh/check it’s a fast as it’s always been. So no, I’m not seeing anything “slow” 
Opening an email taking 10 or more seconds to display even if it’s nothing but text. Seems slow on retrieval. Just generally slower than I remember it in the past.
Absolutely no such problem here. I have 2 emails in my Inbox atm, both with images even, and both opened pretty much instantly, like well under 1 second.
Latest Beta (6.308), OP 8P with stock OOS 11 - but I haven’t had any issues on previous K-9 versions either.
Maybe someone else has an idea, but from my experience all looks good 
I haven’t seen slow behavior either, it seems just as fast if not faster than previous releases.
The annoying bug of not showing new messages when refreshing sometimes makes me think it’s slow, as there is no change to the screen after refresh and I sometimes wonder if it has finished the refresh or not.