I've read about that some time ago. Wasn't that essentially replacing the ChromeOS userland with an Ubuntu userland while keeping the ChromeOS kernel? iirc that seems like a very poor alternative because at some point in the future you'll run into the same kind of problems with this ChromeOS kernel as we are here with our ancient Fremantle kernel on our N900.
In advance: Sorry for the partly German links. I'm too lazy right now to check for English versions. Notebookcheck says the CB30 runs 7 hours with wifi on battery [1]. The same goes for the ES1 [2] and I think 6.5 hours for the V3 [3] still counts as similar.
I don't know the US market. I only checked the German/EU market. Here your CB30 costs 320 Euros. All the alternatives I mentioned cost between 250 and 400 Euros.
That is until Google release an update that renders your SD card useless like they've done with Android 4.4.2 (and probably subsequent versions).