I think Brownie only posted that as a reference for you No need to bring up that whole thread all over again.
Feel free to open a discussion if you would like in this thread here. I'll start by adding my 2 cents.
IMAP is a sound idea. Unfortunatly, from a technical point of view, it is a bear to implament. Basicly, it forces the IMAP server to handle about half of the tasks that are normally performed on the client machine by the client. This makes it resource intensive. The other thing about IMAP is that it maintains a connection to the server, unlike POP3 which just downloads the mail and closes the connection. In other words, it is VERY resource intensive. (VERY VERY I should say, in my personal experience anyway). If you get 10 clients using IMAP on a server, it will take a nice chunk out of your processing time.
The other MAJOR (down/up)side to IMAP is that is stored all the users mail on the server, until they delete it. Now that mail is stored in the home directory, this means that all the users mail (until they delete it) will be counted with their quota. This is convient to the user, because they can access the same mail everywhere, and you may think if it counts against their quota, who cares, BUT they will e-mail you everytime htey fill up there quota with mail and it may become a serious support hassle.