Perhaps not better performance (although they did promise that, but let's just chalk that up to marketing), but for other reasons, it's still a win even if it delivers poorer scaling than the official ATi/nVidia solutions:
1. You can crossfire/SLI with two cards that don't have to be the same model. For example, you can't SLI your old 9800GT with your newer GT285, But that can work in Hydra.
2. You can even mix ATi with nVidia cards. For example, you have a GTX260. You jumped on the ATi 5xxx bandwagon and got yourself a 5870 (lucky you). You don't have to throw you GTX260 away. You can use them both in Hydra.