I'm curious. Setting things like this up is my idea of fun. I use the same technique for my business. I like static site hosting, and liked the idea of things being speedy no matter where our customers are. Cloudfront does that well.
As far as cost. I'm 30 and I don't like relying on free things. Github probably wont go down, but I'd still rather pay. I set that up Dec 1st, served 100k pageviews. My Amazon bill right now is $1.25 (one dollar, twenty five cents). Maybe that'll go up, but for what I'm doing, I doubt it will be that expensive.
I've run a Jekyll site from S3 with no difficulty, at a satisfactorily low hosting cost. Cloudfront takes only minutes to setup, and the costs are competitive, so I imagine it's a promising route.