From Team-Xecuter.com:
[QUOTE]
What is Fusion?

Fusion is a hacked devkit kernel that runs on retail RGH hacked consoles. Think of it as a modified OS for your xbox console. It brings you all the features and capabilities of a real devkit without all of the annoyances. Fusion is more powerful than any normal devkit or modified retail console. It is designed for both developers, and gamers, bringing the best of both worlds together .

For Gamers:

Fusion may be designed on a kernel made for developers, but there are many features exclusively for gamers:

-No system-link ping limit, can also system link with both retail and devkit consoles
-Can use both retail and devkit gamer profiles. saves, and game content
-Boot straight to your dashboard of choice
-No restrictions on games or content
-No region checks
-Arcade games are fully licensed all the time
-Multi-disc games can be ran off the hard drive with no insert disc messages
-Built in trainer launcher
-Can easily boot xell, trainer launcher, and settings manager via custom tab on xbox guide
-Games copied to hdd via dashboard no longer need the disc in the dvd drive to play
-And much more