Now that it is pretty much confirmed that Valve is working on Steam on Linux, this is probably not much of a surprise. However I just noticed that Steam is in fact sending the right Wine version back to Valve:
The hardware survey just came up in my Steam client and that was part of it. I'm sure they've been doing this for awhile, but this is the first time I've seen it in the hardware summary before clicking "OK". How long has this been happening?
Operating System Version:
Windows XP (32 bit)
Wine version: wine-1.5.4
Crypto Provider Codes: Supported 323 0x0 0x0 0x0