Disclaimer: it's my service. I'd love to answer any questions you have.
Let me try to figure it out: people that can code a static page and use a static generator (know markup languages, maybe tempting languages, can use the command line) and people who can't use an FTP app and haven't heard of Git/Github pages.
How big is the intersection of these sets of people? I would be surprised if it's more than a handful.
I'm not trying to sound pessimistic ... I would be happy, in fact, to know that I'm wrong. So, if I may ask ... do you have more than 0 customers?
I would also add S3 to that list. I host my (admittedly low-traffic) blog on S3 with CloudFront as a CDN for <$2/month.
* What's the maximum upload size?
* If I want to change just one file later, do I have to upload my whole site, or can I just upload that one file?
* Can I make changes as often as I want?
If you change just one file, you can upload a whole new zip, or use the command line tool with has a more intelligent sync mechanism.
Yes, you can make changes as often as you want. :-)