Flash does worth it! Depending on what you looking for. There are now Evolve, RennTech or Mega-Speed all pretty much equaI. I used to run JBD myself so I can compare them pretty closely. The flash will NOT make your car go faster over JBD, (only past the v-max) it will deliver that power differently and everywhere. You will have more like a gas feeling to your diesel if that make any sense.
Retired: 2005 N52 E90 330i Sport 6AT
Retired: 2007 N54 E92 335i Sport 6AT
Current: 2012 M57 E70 X5 xDrive35D