I had a Raptor as my system drive before I got my SSD. The Raptor was a little better than a regular drive. The SSD is much better than the Raptor. If you can afford an SSD big enough for your entire OS, use the Raptor for data storage.
Indeed, I had a 74gb raptor and went to a 60gb vertex 2 ssd. difference is like night and day.
Just remember to check bios options and set the controller to AHCI mode if it's not already, that will give a nice speed boost too although you will need to reinstall windows if changing that without it being a new drive.