Whenever you use their service you are automatically connected to their fastest server.
It basically obfuscates your making it undetectable to governments and ISPs.
OpenVPN is open source, but it requires the use of a third-party client and is more CPU-intensive.
And of course there are very few servers to choose from, which hinders your ability to find a fast server for torrenting near your location.
However, they do not indicate how many servers they have.
Moreover, you can only connect to a country, but you cannot select a server yourself.