There are two downsides. One, battery life sucks. Relative to a Macbook, it's very bad. But, this isn't a surprise to most people. Second, the touchpad driver is shit. Oh man, does it suck. Palm rejection doesn't work, and I had to enable a setting which disables the trackpad for a few seconds after a key press. Otherwise, it's unusable. That part, is irritating.
Those downsides don't really matter to me, because I'm plugged in and docked the majority of the time. I've considered looking into the touchpad issue more, but it's just not worth my effort atm. Otherwise, it's a great machine!