I find Blogger and the other online wysiwyg style systems to be too much of a hazzle to work with. I wasn't aware of github pages, but it looks really nice. I will probably find some inspiration there. From what i can tell github pages lets you create an arbitrary website structure with arbitrary styling, whereas the goal with gcp.com is ease of use and a nice standard layout (sort of like latex). That is also why i haven't added header and footer support, but i should probably make some minimal customaization available, like name and tagline.
.textile is sort of a convention for files with textile markup. I could add support for other markup formats. What would you suggest?