I use Vimium and I like it, but it's crippled by Chrome's extension model. Extensions aren't really part of the browser, they run in the context of the page you're looking at. This means Vimum's shortcuts don't work on the new tab page or when viewing PDFs, and they're unresponsive when repeatedly changing tabs. I'm trying to switch to Firefox + Pentadactyl, which seems much less hacky, but there are enough differences to make the change difficult.
