Depends on the game type and the game itself. Many games (dependent on your system) will only do the initial read from the hard drive on load-up and run strictly from memory from there on out. Raptors are very good drives but any drive, whether it be IDE, SCSI or SATA with high speeds and low seek times are very good.
Personally, most of my gaming is still on 7200RPM IDE drives but as I said, these games are run primarily from memory once loaded.
Your biggest kick will be in initial loading times so decide for yourself if the extra cash is worth it to you.