For those of you who are cerious my steam name is "Crust20" without quotes i have the same avater on steam as i do on xfire.

BTW, the Steam platform incudes many free 2 play games and automatically updates and patches your Steam games (by default - optional.) Many of the free games are NOT Steam exlusive, but some are.
Examples include:
- Star Trek Online
- DC Universe Online
- Team Fortress 2 (Steam exlusive)
- APB Reloaded
- Microsoft Flight
- Alliance of Valiant Arms
- Global Agenda: Free Agent
- TrackMainia Nations Forever
- War, Inc. Battlezone
- World of Battles: Morningstar
- Super MNC (Monday Night Combat)
- Pandora Saga: Weapons of Balance
- Stronghold Kingdoms
- Fallen Earth Free2Play
- Realm of the Mad God
- Brawl Busters
- Magic: The Gathering – Tactics®
- PoxNora
- EverQuest® II Free-To-Play. Your Way.™
- Bloodline Champions
- Iron Grip: Marauders
- Rise of Immortals
- Rusty Hearts
- Puzzle Pirates
- CrimeCraft GangWars
- Champions Online: Free for All
- Spiral Knights
- Forsaken World
The following are Free if you already own a Valve "Source Engine" game such as any "Half-Life 2", "Counter-Strike: Source" or "Day of Defeat: Source":
- Synergy (HL2 multi-player mod)
- Zombie Panic! Source
- (and many more Source mods)
Also note that games that are compatible with Apple Mac (increasing number) are available to play on both platforms through Steam.

These are just a few that I know of at the time of this post. Steam has many more features similar to Xfire such as chat, voice chat and, as Crust20 mentioned, a very mature store and update platform. The store inludes DLC for games that support it.
Steam also has a "Steam Workshop" feature that allows you to create custom content, for games that support it, that you can SELL. Steam also allows you to Trade and give games and custom content.
And of course Acheivements for games that support it.

BTW, on the topic of Free games, here are some non-Steam Free-to-Play games that I know of that you may want to review:
EA Free2Play Games:
- Battlefield Heros: http://www.battlefieldheroes.com/
- BattleField: Play4Free: http://battlefield.play4free.com/
- Need for Speed World: http://world.needforspeed.com/
- Warhammer Online: Wrath of Heroes: http://wrathofheroes.warhammeronline.com/
- BattleForge: http://www.battleforge.com/
Hi-Rez Studios Free2Play Games:
- Tribes Ascend: http://ta.hirezstudios.com
- Smite: http://www.smitegame.com/
- Global Agenda: Free Agent (also in Steam): http://www.globalagendagame.com/
Aeria Games: http://www.aeriagames.com/games
- Repulse: http://repulse.aeriagames.com/
- Shaiya: http://shaiya.aeriagames.com/
- Wolf Team: http://wolfteam.aeriagames.com/
- Realm of the Titans: http://realmofthetitans.aeriagames.com/
- (many more)
Other Free2Play Games:
- Blacklight Retribution: http://blacklight.perfectworld.com/
You may also want to try playing free demos of games, no download or installation required, you play in the "Cloud":
http://www.gaikai.com/

I hope you at least one of these fantastic games.
Enjoy!

- CaptainMorgan
http://steamcommunity.com/id/CaptainMorgan

I found a Steam Community Forum that maintains a list of teh Steam free games here: http://forums.steampowered.com/forums/showthread.php?t=851573