Outlook.com now has IMAP access support as well
(Trying hard to remember why we might care. I use Microsoft Outlook Connector.)
this thread from these forums a month ago, the OP really needed IMAP access, and now he's got it.
Some of us like to set up email access the old fashioned way (imap or pop3).
And some of us don't use Outlook. (I'm guessing that Outlook Connector won't work unless you have Outlook.)
Monolithic - if it breaks, you loose everything.
Monlithic - if you have a large file it takes time to backup
Not easily accessed by other clients - you are locked into the MS ecosystem. Also does not support x-platform access.
IMAP vs POP (I use both, but incline to IMAP)
Largely depends on how you want to manage your e-mail (once you've decided you don't want to be locked into MS-Exchange)
Do you want your e-mail archive to be on your mail server.
Are you using a client or web interface.
Do you want to keep emails on your client/s.