I've been told that using a RAID is better as you have more disk heads doing the io and have the fall over safety. We've had the TempDB on a separate drive as well for a while, even put the log files on a separate drive, but it's much esier to manage and safer if they are on the RAID. After a hard drive failure it's a simple recovery.

This is off the plot of how to measure the TempDB usage.

What platform is this on?