After the upgrades today, I was quite disappointed with disk speed. It seemed no matter what I did, the generic-ide module was taking over my drives before the specific (piix) module could load them. While it did allow me to access my data, it was extremely slow, and I couldn’t turn on DMA, no matter what. After much headbanging, several reboots testing different options and attempting every known way to load the module, I finally went back to my last kernel which worked perfectly.
It appears the 2.6.15-1 and associated udev scripts have a problem where ide-generic is loading first, no matter what. I found some debian threads where they want to get this fixed (they are in the -5 range) by .16. Hope they do.