I google far more often than I ri.
http://www.google.com/search?hl=en&source=hp&biw=101...
Personally, I can switch to a browser window, google for a gem, find its docs, and read them online in less time than it takes for ri to return its usually incomplete result or ask for brain-dead disambiguation. Ruby would have a better reputation if ri simply didn't exist.
I can't say I've ever used ri, although I do browse local rdoc, sometimes. I know plenty of developers that hadn't heard of "gem server" until I mentioned it. And this is completely discounting production environments, where the documentation is almost certainly a waste of deploy time.
It's an orthogonal problem, though. The main issue with doc generation is that it is really, really slow (compared to the rest of the install process). If it can be sped up – patches are surely welcome – it'll just leave the envs that flat-out don't need the docs, ever, and those can use the new --no-doc.