If there hadn't been the left picture for comparison I would have thought it might even be ok that way.
Until I saw screenshots from SuperTuxKart I also though that this "texturing" they use would be normal. But in that case it's the same problem in Windows.
I run fglrx at the time when my 3870 is in since fglrx has matured power management. Without that an the onboard 3300 I don't notice that much difference.
The free drivers seem to be partially even better in 2D, esp. since fglrx 10.7 made a mess in 2D scrolling so I had to revert to 10.5.