A few reviews says that they are one of the best one (PIA) concerning anonymity. If you use shared IP, then there's no was they can keep logs. And for now, the bill hasn't passed yet about data retention in the U.S. (though that might come in sometime, but I hardly see how you can keep log for shared IP VPN). When you use that, then what happen is that multiple users are set to this external IP. So the only way to track you is if they keep log of EVERY packets sent, from which customer, with which re-mapped TCP port number. Technically unfeasible for more than a few hours.
Dedicated IP is another story though.
Another one is BolehVPN, based in Malasia. But they are twice the price of PIA.
Both accepts Bitcoin payments.
A good review site is
http://www.greycoder.com/best-anonymous-vpn-for-2013/I personally use PIA. One good advantage with their client is the kill switch. As long as the client is still running, if you get disconnected, then it kill your Internet access. It can also re-route DNS lookups (DNS leak protection). So it use *their* DNS for all your queries instead of your own default DNS.
Make sure if you use VPN that you check their policy for torrenting. Both PIA and BolehVPN ask you not to use U.S. servers for torrenting. They have a list of servers you should use for that.
One advantage of Boleh though is that you can select fully routed server. So you can forward every incoming port (useful for torrent). With PIA though, you can connect to some servers that forward 1 TCP port only. Although you have to re-configure your torrent client incoming TCP port each time you reconnect to a VPN server. If you leave your VPN connection active, it's not as bad as it look though. Though the fully-routed BolehVPN servers are dedicated IP (that's why they can forward all ports back to you).
I did try both, and even chained 2 VPN back to back (just to test if it would work... that was a pain, using multiple virtual machines, but it worked!).
