As far as I've seen, it appears that all nVidia GeForce and all ATi Radeon cards will indeed actually be supported under Vista and DirectX10, but will largely all be "rated 1," at least for the ones without SM 2.0 support. None of them, it seems, have support for SM 4.0, though rumors persist of fragments of such support in The GeForce 7, and especially Radeon X1k cards, particularly given the latter's connection with the Xbox 360's Xenos GPU, which does clearly contain some things that could crop up in SM 4.0. However, they would not likely be worthwhile; better to wait for the GeForce 8 and Radeon X2k cards, which should clearly bring out DirectX10 support at the full level. Of course, it seems that said cards won't work outside of Windows Vista...