This was my second attempt to get email working on Emacs and I gave up the first time, too. I persisted this time and I _think_ it will pay off. There is the obvious danger of this becoming another "project", but I'll make a note to check-in again in six months. It's an experiment!
I've not seen the other things you mentioned. I only check for email every 10 minutes, but opening and (especially) searching for emails seem much faster than doing it in Gmail. Plus, I can do searches across email accounts, like all unreads across all three accounts. That was definitely slower in the online clients.
Finally, there's a quick ('a' then 'v') way to just open a message in a browser if the HTML is too thick.
I've not seen the other things you mentioned. I only check for email every 10 minutes, but opening and (especially) searching for emails seem much faster than doing it in Gmail. Plus, I can do searches across email accounts, like all unreads across all three accounts. That was definitely slower in the online clients.
Finally, there's a quick ('a' then 'v') way to just open a message in a browser if the HTML is too thick.