Varnish would have been fun to play with for a static blog. For one thing you then could use ESI to not have to invalidate the cache as often.

But I disagree with one thing — the "git push → deploy dance" is a pro for Jekyll! ;)

I have found it to be fun the first few times, but as your blog grows I've found it to be a pain to deploy every time I make a small correction. Also, with markdown there are always corrections to be made for formatting purposes.

I was watching a demo of Jekyll and Octopress pushed to github at a user group meeting. As a demo, the presenter made the requisite small change, committed, and pushed.

5 MB of upload later on a clogged wifi link, it was up live. Admittedly, that's because the generation was done on his laptop and pushed up, not done on the server side. But 5mb and a ton of rendering time is going to suck if you're ever changing things for formatting, or edit anything.