I come from the E90 and there i had profimail.
And man what is that program way better then Modest. Its not even close but a very wide gap.

Of course it is for me the most part is Imap-Idle, not using the sent folder on the server also the user interface is something that i dont like. Why for example does the send button scroll outside of the screen (yes i know ctrl-enter will also work) and instead of the most important button (send) we have completely unimportant buttons on the screen for altering text (size,bold) those are a waste of space! never use them at all!

And this one for me also (for others it is just the reversed i think but make it a preference) i want to alter the font size of the list to way way way smaller, Why can i only see 5 entries?? If i open tmo in the browser i see way more topics in 1 screen, including much more info (like the first line of an email i already want to be able to read).
Also when i am in a mail, and i delete a mail, i don't want to go to the next (or previous) mail! i want to go back to the list.

Also it generates way to much traffic, if i send/receive an account and i dont get any new emails then it did tranfer more the 300KB of traffic. I dont mind that to much when i am in my own country. But in a foreign country that it really expensive. With my E90 and profimail, i just had profimail in a imap-idle configuration and that didnt generate much traffic at all. (the mobile java gmail client is even way better! there i can read many many mails and i only have 60-100kb of traffic)
It seems that modest does get constantly all the id's of all my mails in the inbox.
and i guess thats also the thing that makes Modest slow to use. it has to handle all that stuff.

I also want preferences how many mails it should keep in the inbox (or any folder)
something like i it can store the last 500 subjects (per folder) and the last 100 it can cache the whole message including body.
A preference what to do with new mails (only get the message subject or get the whole message)

If needed i can go on and on. Problem is that that for a mobile computer i expected that email was on the same level as the browser or the IM (those last 2 are really great but the Modest is the worst part even more worse in my eyes the Ovi Maps 1.0)