So I discovered Jekyll a few months ago and ever since I've been wanting to move my blog from Tumblr to Jekyll. This site is super tiny (planning on adding stuff though) but having it all under one roof is much better than having my blog hosted somewhere else. Also you never know what's gonna happen to Tumblr now that it's owned by Yahoo!.
Now I have full control of my blog and I can customize it however I want. Not that you can't do that with Tumblr, but it reminded me too much of those MySpace days where you had to enter your css in that editor box.
With Jekyll you can blog using HTML or Markdown which is what I suggest you use. Like John Gruber says "HTML is a publishing format; Markdown is a writing format".
Jekyll is awesome so far, and not only for blogging but the templating system it has gives you the option to have a nice modular working site. I think I'll do blog/tutorial on how to use Jekyll to create a modular site. Stay tuned.