Along with my various Arch Linux systems, I've used a Chromebook (Samsung Series 3) for a year now. It pretty well has done "what it said on the tin" and I've definitely used it more than I thought I would - often because of the superfast boot and for "just having a quick look" at something on the web, or checking emails. And of course, battery life has been long (5-6 hours).
Many web apps for Chrome have been pretty good - some excellent - but Google really do need to prioritize a few more basic necessities, such as the ability to connect MTP and PTP devices.
Also, the mandatory updating of the OS cannot be stopped, which is tough luck if it starts updating when you're on a dodgy wifi signal and just about to go on a train/plane, etc!
Good-ish+, but not quite great yet.