I am using a Velicoraptor for my OS and all FS related stuff, and I am very pleased with it. Since it uses a 2.5" form factor, it runs much cooler than regular hard drives, and as long you keep some form of airflow on it it will be fine. I rarely hear it too - the one exception is when loading huge amounts of data, like when I start the OS or load a flight in FSX.
Because it runs at 10,000RPM, the textures, especially in FSX, load much faster. There is a noticable difference between my old 7200RPM drive and the VelociRaptor. Considerating it is only $200 now (it was $300 when I bought mine) it seems like a good choice for gamers who must load large amounts of data.