The main bottleneck in nnimap/gnus right now is imho that it takes a
long time to check for new mail. No other imap clients I've tested
does this at all, so perhaps we can make that part optional. (It can
also be made faster by using a different strategy).
OE4&5 check for mail in all subscribed folders. They do it radically faster
than nnimap does.
The major bottleneck would then be that it takes a long time to enter
a folder, this is impossible to fix without heavy modifications of
Gnus, and for me this isn't a major problem anyway (entering a folder
with ~1200 articles takes ~25 seconds with 9s spent in nnimap for
me. I can live with that).
OE4&5 gain speed advantages on this by caching the headers.
Do you agree with my observations of where the bottlenecks are? Which
things in nnimap are slow for you?
The slowest/hardest thing for me is finding an old email. ;)
--jrp