You guys are absolutely right about performance. However, a benefit of readyboost should theoretically be less wear and tear on the hard drive. I have been studying SQL server configurations and a common mistake is failure to plan for a separate drive for tempDB. So, admins sometimes burn out the drive that stores the important long term data by sharing it with transient data. Currently I use an 8gb USB for Readyboost and TEMP files (for personal computing NOT SQL Server of course! LOL). Although with SSD prices coming down, I may go that direction soon.