I actually just wrote up a blog post as well about why I don't like feature branches: http://www.pgrs.net/2011/08/29/why-i-dont-like-feature-branc...
My main reasons are that git history gets messy, builds don't run on feature branches (although github seems to have a work around here), and refactoring is harder.
My opinions are largely based on working on larger projects (more than 10 devs working in the same codebase).