[ColinM]

Passkey is not client picky. That being said, some clients are better than others.

I got this list from another tracker and it has held true most of the time. In my opinion:

ABC - Randomly reports bad stats to the tracker.

Acquisition - Not a proper Torrent client.

BinTorrent - Users caught cheating with this client.

BitLord - Based on old buggy BitComet code.

BitSpirit - Randomly sends DHT packets to its own public tracker.

BitComet - Very very popular client but EVERY version reports bad stats to the tracker.

Bittorrent++ - Does not uniquely identify itself.

burst! - No longer maintained.

CTorrent - Communicates with the tracker incorrectly (aka not following BT spec).

ed2k - Not a proper Torrent client.

eDonkey2000 - Not a proper Torrent client.

eXeem - Not a proper Torrent client.

G3 - Consistently reports bad stats to the tracker.

MLdonkey - Not a proper Torrent client.

Qtorrent - Does not identify itself correctly.

Opera - Not a proper Torrent client.

Shareazza - Not a proper Torrent client.

Torrentstorm - Development and bug fixes ceased 30th March 2005.

Torrent Station - Does not uniquely identify itself.

Turbo Torrent - Rumored to do bad things.

XBT Client - By default does not identify itself on the swarm or can be configured to pretend to be another client.

Ziptorrent - Does not identify itself correctly (specifically it lacks version number). Being used principally by spoofers, taking advantage of this bad code decision.