- Excellent Ping
- Channels and Chat in-game
- Ladders and Rankings, secured against cheating.
- Extended stats, with possibility to see who D/C etc (source)
- AMM-type Matchmaking
- Avatars, Images and Icons to represent yourself
- Diablo III Hardcore mode
- Friends/Ignore Lists with advanced management (see accounts below)
- Clan Support
- Automated Tournaments
Looks pretty good to me!