The changes Andy committed regard modularization of pata_ali - nothing more. As I underestand correctly you use pata_ali right? And if it reports the errors you mention in bug #591532 , than it seems to be pata_ali issues and I believe they have not much to do with making pata_ali a module - the modulatization should not cause them.
As far as I know ata_generic is reported to poorly perform on some hardware, which confirms your performance issues with ata_generic enabled.
I'd gladly investigate these errors of yours - perhaps they'd appear in my system too but unfortunatelly I'm too scared to switch to Lucid right now because of bug #585765 which affects at least one of my systems. Until it is solved I'm not even touching Lucid.