If you want fast unzips or copys, forget running swapfiles on the main drive at all- get a second drive just for the swapfiles.
using a file of size 844,779,600 (0.8GB) I copied it from one partition to another on the same drive, first with the temp folder on the same drive, then with the temp folder on a seperate HDD. I also tried it on a raid 0 array, with and without the seperate temp drive. Here are the results.
Drives: All IBM 60Gb GXP120s OS: XP Pro, Mobo: Asus P4S800 Raid: Promise tx2
Single to Single, Temp on single: 2min 35sec
Raid 0 to Raid 0, Temp on Raid: 2min 16sec
Single to Single, Temp on Raid: 0min 41sec
Raid 0 to Raid 0, Temp on single: 0min 38sec
Quite a difference eh? All from adding a seperate drive as your temp. As you can see, raid makes a small contribution (not much tho). I did try to put 2 raid arrays in so I could test Raid 0 to Raid 0 with the swap on a seperate raid 0 but the drivers would not play ball and the system was unstable.
I have not tried it, but with results like that, I feel that even an old legacy 5400 speed drive would boost performance, if thats all you have.
Certainly beats farting around defragging or re-aligning your swapfile here and there on a drive.