Depends on what you want, of course. I put a full Ubuntu distribution on mine, along with a full numerical stack (anaconda python + Octave), git, ruby, perl, etc., and am happily programming away. I grant you that I am not the customer that Google is targeting, but I find it very capable. I am already working from the cloud - all of my python and data resides in Dropbox or a BitTorrent Sync folder, and I just work from them regardless of what machine I'm on.
It's an interesting tradeoff. You will obviously not be putting a first person shooter game on one of these, or installing massive software stacks, but I don't really want that from a ultrabook anyway. I'm overjoyed with mine (I have the cheap Toshiba, not the Pixel). If I lose or break it who cares, I'll buy another. Meanwhile I have a portable ultrabook that I can develop on, keep up to date with the office, or just take to bed to do some light browsing. It's utterly fantastic in a 'less is more' kind of way.
edit: so far I am only using the Dropbox stuff with the chromebook - I do not know if can use BitTorrent Sync from it, and I may have to revise that part of my workflow.