It's not free, that's true. But it's very cheap, especially when paired with Amazon's 1-year free usage tier. But the main benefit is the added control over the web server.
The main benefit you mention is the biggest disadvantage of this solution as you may need to scale it as traffic grows. You can avoid it by using S3/GH Pages.
I actually found that GitHub Pages didn't scale well at all -- during peak traffic, response times slowed to over 10 seconds. This was my main motivation for the switch. Nginx (even on a micro EC2) should be able to handle very high load without the need to scale. S3 is definitely a viable option as well (and I'm not suggesting you shouldn't use it) but I find that an EC2 was a better fit for my needs.
Great article. One thing I'm struggling with as a freelancer is finding clients - I'm based in a small town in New Zealand, so I'm a long way from the opportunities in the UK and USA. How do you track down and approach new clients (who are likely to be happy with your rate)?
I also feel like being in New Zealand hampers my ability to charge a higher rate. I don't know for sure, but I suspect that companies here are used to paying lower rates simply because there's less talent here than overseas.
It sounds trite, but have you tried contacting companies in the UK and USA?
If written communication between you and the client is strong, it's often an advantage to the client to have someone working out of sync with them. At the end of their day, they dump some stuff into $ISSUE_TRACKER_OF_CHOICE. When they get back the next morning, it's done.
It's harder to do, but you don't even need to be in same city. Build a strong portfolio, for us it's several good projects on Github and jobs will come by themselves.