It appears that Google is now offering IMAP on their email accounts. Although POP3 support has been in place since late 2004, the one key element that was missing was the Internet Message Access Protocol.
This has been a missing feature that has been a barrier for many potential users looking to migrate to google mail. With the introduction of this feature users will be able to access and interact with their inbox from multiple devices (PC, Laptop, Mobile, PDA). This provide users with more flexibility on how they manage and manipulate their inbox, no-matter which device they choose logon from.
This sole feature could be the element that opens the door for Google where business customers are concerned. As part of their Google Apps (http://www.google.com/a/) for Businesses, Gmail is thrown in, as part of the bundle.
While POP3 was the only method for retrieving emails from devices unless you used the Ajax-rich online client, the users' experience was somewhat limited.
I doubt if I'd be wrong in saying the targetted/potential audience for this protocol is more within the business sector, moreso than your standard home user.