ATI's Vista drivers have been far better than NVidia's in a number of ways. NVidia is still struggling to make the drivers for the 9800GTX stable under Vista. It took them three updates to fix the DirectShow problems as well.
That aside, the CCC can cause most of the problems with the ATI drivers. Not installing it will result in a far more stable experience.
Another problem for the 4870X2 cards is people using poor quality power supplies and stuffung them into cases with poor ventilation (45 fans in a case does not gaurantee good ventilation). It is sensitive to noise. Maybe more so than other cards. A more costly 16 or 20 layer PCB might have helped solve that.
Overall, at this very moment, both NVidia and ATI are pretty much equal in driver stability. Both companies have problems with the latest release of drivers. With NVidia or ATI you have to be careful about what version of the drivers you use with the product. A 6000 or 7000 series NVidia product does not run well under any 1xx.xx driver, as an example. ATI's 9000 series products run best under the very old Catalyst 4.12 drivers.
Do not take noise levels at a fan site as a solid indicator of any problems with any hardware or software. I can point to other fan sites who are ready to hang the engineers at NVidia. Fan sites lack objectivity and every little issue is the end of the world. It is the nature of the beast.
I have a Sapphire Toxic 4870X2 at home and it has been rock solid stable.