I start to use CDN from April 2010, with MaxCDN. Here is the first post I mentioned it.
Later, I moved to Amazon, FrontCloud in August, 2010.
For some reason, I move back to MaxCDN. I start to use MaxCDN again from last week.
It is easy to implement MaxCDN.
The price is good, if you have a big volume or bandwidth requirement.
You can have One TB = 1000GB for $39.95.
And 30 day Money-Back Guarantee
No Monthly Fee
If your customers are mostly in North America, it is the one of the best choice.