Definelty SSD is the way to go for main OS and app drive huge boost however I would still stick to standard drive on SATA2 say 7200rpm drive with good cache as my data drive. If custom building then get two and mirror them. Then on top once built just image the SSd drive to ensure if it does fail roll back is easy. For the gains its great but I wouldn't use it as my only drive.
F30 335i M Sport