PiXELHD is a pretty new tracker. The tracker was made for those people who downloaded the encodes of the PS3-TEAM. They were internal encoders at HDME, but decided they wanted to make their own tracker.
The userbase is really small ATM, but a lot of the PS3-TEAM encodes have been uploaded already. Encodes from a group called iCandy is also internal there, but it is mainly PS3-TEAM encodes you will find