1) Wider game support;
2) Chat support above forced fullscreens (more of a business issue presented by paranoid game devs); and
3) Cross-platform support.
PC, PS3, PSP, Xbox 360, Wii, DS, Windows Mobile, Symbian, Palm -- I want to see all gaming across all platforms on one Xfire account.
Think only PCs have the flexibility to preload resident apps beneath games? Think again. Gameshark preloads beneath my PS2 games. I hear the Xfire guys are already working on something for the PS3.
My previous advice to Philippine game publishers stands. If you're going to publish a localized version of an Xfire-supported game, make sure the installation directory and primary executable filename match those of the international version. These simple considerations will ensure seamless compatibility with Xfire.
Don't be afraid Xfire will kill your ability to bullshit. You simply can't afford not to be on what some call "the next MySpace".