Octopress is a blogging engine on top of Jekyll. It got my attention since it provides themes and a layout that looks great on mobile devices, too.
I had been playing with the idea to do my own simplistic theming long enough to realize that I would never do it. The other feature I like is its plugin system: some I’ll use right away (e.g Github style codeblock) but I also like the idea that I can write a plugin for any specific need that might arise later.
I had had my blog on Jekyll so migration was not really hard. I hit a few minor roadblocks on the way but documentation is great and the author, Brandon Mathis was really helpful on the support forum so I could eventually sort them out.