I believe most of the Steam Linux games available are native ports and don't use Wine. Maybe there are some that do use Wine, but I don't imagine that they will make them available through Steam unless they are confident that they will actually work.
So the real question here is, "what is the real value of this assuming you already have a dedicated Windows PC or a dual boot for gaming?"
For myself it is nice to have a few good quality indie games available to play if I fancy a short break from coding on my Linux box without having to power cycle my PC. For serious gaming sessions Windows is still king for now.
The real question is about future games. There seems to be increasing interest in cross platform toolkits for game development, this is probably most because people want to target iOS and Android rather than Linux however.
However if it gets to the point where Linux just becomes another output format for a cross platform game engine (like unity3d) then perhaps you can expect future game titles to become available on Linux simply because the friction to launch on the platform is so low.