The idea of an RSS feed for a single users activity is a great idea and I could see it being very useful as a way to track everything that a highly active and productive user does, or a way of displaying your StackOverflow activity on say a blog or something like that.
However, currently it's kind of hard to use because most of the entries lack context. If I update a question or answer it just puts the whole question or answer back in the feed and doesn't mention that it was just an edit or change. I know I can compare the published date to the updated date, but why not make this consistent with the way answers show up in the feed by being prepended by "Answer By User"? Couldn't it have "Update By User" for the updated entries
In addition is there a reason comments are not considered part of User activity in the feed? A lot of people's comments are just as valuable as answers and I'd like to keep up with those via RSS as well.