I tried it with a single account, the UI is nice but I kind of prefer a more dense UI for email. I'm probably just really used to Airmail's UI, it's similar to what Sparrow used to be and I felt that was approaching perfection at the time.

Also the memory footprint was a little large but that's understandable since it's built on Chrome/Node. Web browsers and development related processes (mostly Ruby) are my top memory consumers right now, I'd rather not have my email client join their ranks.