Of course, MMOs require a server or they ain't MMOs.... but I would much rather use the native client / server than go thru Steam. For example, my 14 year old son was disappointed when he didn't get into the WoW beta ... at the time our business was doing a lot of beta testing for PC utilities and other software and sent our "resume" to the developers of another game called The Saga of Ryzom. He "got in" and I set up a toon for him so that it would be ready when he got home.
He, his brothers and I played for about 2 years and though I take 6-12 month vacations, i still find myself going back.... and yes, with 63 skills that can be brought to level 250, I still have things to do in game
The game is available in both 32 and 64 bit versions for Linux, OSX Windows. Two weeks ago it launched through Steam. When I do get a chance to get in game of late, I spend a good part of my time helping users switch from the Steam to native clients, reason being that the former are experiencing no multiple graphics. GUI and connection related issues that just "disappear" with the native clients.
I'll note that I'm moving them from the Steam (win32/64) clients to a beta native client for Win64. The Steam overlay adds additional complications which are just best avoided if another alternative exists
EDIT: For anyone interested in playing the game (free up to level 125, then about $10 a month), you can create an account here:
http://ryzom.com/
The native client is still 32bit as only the steam version has been released in 64 bit. You can get the 64 bit beta clients here:
http://ryzom.kervala.net/clients/