I have a highpoint raid controller on my abit motherboard running a striped array. "Slowing down" has not occured for me. Honestly, it runs like a raped ape.
I have to 80 gig maxtors with 8 meg cache on each. I built the striped array with the bios config.
Before installing xp, I used partition magic and split my 160 gig partition into the following chucks.
20 gig/
20 gig/
80 gig/
20 gig/
This allows me to keep my c drive (O/S) to a small size, that I ghost over the network using ghost corp edition. I also defrag on an often basis, and have had very good performance. Hope this helps.
Sidenote, the only thing I found hardware wise that doesn't play with my p4 abit board is the "intel application accelerator". It down right slayed my machine, so I reinstalled my last image of ghost.