Version control is a must if you're serious about software development. Like it or not, you have to be serious about software development if you want to build a large computer vision system (and perhaps get a PhD while doing it). Over the years, I've moved from CVS to SVN to git. I refuse to code without version control.
While git lets me easily share my private research code with my colleagues at CMU (much easier than svn), github lets me 'publish' it online in style. This is not the kind of sharing that most researchers do -- most researchers I know just put a tarball online. I've started playing around with github, and I'm really excited about using it for my own Computer Vision project.
I think sharing research code in a high-quality environment is necessary if we want to push the boundaries of machine intelligence in a team-like fashion. I think good papers and good code make good research, and while lots of care goes into high quality publications in the field, very few high-quality object recognition programs are published online "well". I think having forums, version control, wikis, etc is important if one wants a project to stand the test-of-time. I think github is the way to go if you're going to share your code online.