I moved my mail there, simply it rocks!
The conversations style takes a little bit of getting used to but there spam filter is also FANTASTIC. I really like the search but it lacks partial word matching, crazy but if you have a gmail account now you know all that.
I also set up temporarily setup evolution (thunderbird or whatever would do) with both imaps and drop and dragged about 2GB of mail, not saying that was fast, but it worked
I also thought I would go back to my normal imap client but didn't the interface has really grown on me. In addition being able to specify other email accounts and automatically pull that mail into one with tags and labels to slick.