My first reaction is "if it ain't broke, don't fix it".
When I've heard of or seen probs, mostly they had to do with optical drives not working. Doesn't seem to be your case. I use win98se, although I set up a dual boot system with XP to check out the OS. I noticed on two rigs with XP that the SWE IDE drivers made all drives show up as scsi devices. I thought wtf??, but there was no real problem.
As far as they're being slower, maybe a benchie would tell. Don't know which to suggest, at least not any of my HD benchies cuz they generally use their own drivers so wouldn't point out probs with thw SWE IDE drivers.
But that seems like a lot of trouble for something that's at least not a noticable problem. Anyway, I hear peeps saying they (SWE IDE) have improved.