Vista-only DX10 a mistake

...according to Valve's Gabe Newell in an interview for heise online.de:

According to an online survey by Valve Software, only one in fifty players who access download service Steam has a DirectX 10-compatible graphics card and Windows Vista installed. In an interview with heise online, Gabe Newell, president of Valve Software, said that Microsoft made a terrible mistake releasing DirectX 10 for Vista only and excluding Windows XP. He said this decision affected the whole industry as so far only a very small percentage of players can use DirectX 10.