Technically, this is probably a feature request, but, since I can't seem to post in the other linux forums, it is going here. I'm a longtime arch linux user (6+ years), and I'm also very new to using Steam (just installed a few weeks ago). I can't help but notice that Steam seems to be designed very much in a "single-workspace" fashion - a window that tries to "stay out of the way" of other windows. Which is great, when all you have is a single workspace. But on linux, I can have as many as I want. Most people run 4 workspaces at any given time. I feel like the steam overlay could be integrated into a custom desktop environment, or Steam itself could be integrated into a larger desktop environment much more efficiently than it is now. The main reason for this would be to bind Steam keys (particularly Shift+Tab) to the Desktop Environment level. The cool thing about linux is that you can play around with this sort of tight integration of software and make it feel really seamless. I feel that it would stand a good chance of improving stability for games like TF2, where I want to pull up the overlay and chat with people while loading a map (something TF2 seems to greatly dislike). While the overlay shouldn't stop TF2 from loading, the DE-level keybindings would allow the user to bypass the instability of the program by attaching the command to a completely different process/thread, and the compositor of the DE would handle the transparency of the overlay, leaving the TF2 process untouched and loading just fine.
This is the kind of stuff I feel that Valve should be playing around with in linux, if they're really interested in moving over to linux as the gaming platform of choice.
Obviously, this presents the potential problem of "DE wars". So please, in your comments, avoid talking about specific Desktop Environments. From a configuration perspective, most of the major ones can be tweaked minimally for this sort of integration. If Valve wanted to be ridiculous bosses, they could build a custom fluxbox or enlightenment DE and have it run on a separate X server, taking integration up a few notches. Valve is full of very talented people, and this post is made in the hopes of enlightening some of them as to what is possible and supportable in linux, things that are simply inconceivable on other platforms.