I did work on an Acer C7 ($200 with about $200 worth of SSD+Memory and a $100 23" LCD when I was home, total cost $500) with Ubuntu for about half a year. I initially bought the machine to travel with, and it became a workstation when another machine malfunctioned. I do a mixture of C, Python, Javascript, and Clojure development. It was absolutely fine. Clojure needed a settings tweak to bootstrap the repl properly (it was slow at over a minute), but I never left the repl, so it was a one time cost. C/Python/JS have compilers that were fast even on a dual-core Celeron. tmux/bash/vim were fast (as always).
I did everything on that machine up to and including playing TFC via Steam. It ran an IRC client, Chrome, Firefox, VirtualBox for Windows, and my xterm w/tmux. I don't know that I'd give up my rMBP for it, but I did a lot of work on the chromebook.
As far as a developer machine goes, a $300 special 14-15" screen plus $200 of RAM+SSD would probably be fine for 99% of what I do. This likely doesn't work for those who need Photoshop, do video editing, or need to rebuild their OS (rebuilding world in FreeBSD on the thing would have been a bit much). If you're slinging JS, Python, Ruby, Erlang, Clojure, Java or something similar and you can't get by on 16GB of RAM and a 128GB SSD, something is atypical.