If you are Korean it's the DREAM tracker, but if you are only interested in English content it's medicore.
What others have stated as negative aspect is really positive for me. I really like their security and even though they just have open sign-ups I still think it's one of the safest trackers.
The speeds are also great for European users(people with a European VPS/server/seedbox), which can't be said about the Chinese trackers.