Why do you want to? Not trying to be snarky, but I've been using various source control tools for closer to 20 years than 10 and I can't remember when I've ever needed or would have benefited from revsets. I'm genuinely curious what problem this solves and whether I've just never experienced or have made my own hodge podge solution for it incidentally.
I am used to working in large repos (>100 commits/day), which generally means that something like 'git log --graph' contains a lot of extraneous information.
The most common workflow I have is that I've got a couple of old working branches (like featurea and featureb), and I want to see if I need to update featureb to a newer head or not, or if featureb was based on featurea or featurea-v2. A demonstration of this kind of thing is 'hg wip' here: http://jordi.inversethought.com/blog/customising-mercurial-l....
Another thing I would use revsets for is answering queries like "which of these changes that's on the public repository made its way into the internal repository (which periodically merges from the public repo)?"
