I would honestly say to try out Metz flashes. I'm currently using the 48 Af-1 and the 58Af-2 with my Nikon and Pentax cameras (dedicated for each). They're sturdy, powerful and less expensive than Nikons. In fact I leave my Sb900 at home and use the Metz when I'm shooting in ruggged areas since they feel less delicate. They also do well with I-TTL and can be used in CLS (warning: the cheaper flashes can be remotes but NOT commanders!).
And to top it off, you can update the firmware on the flashes quite easily thru their site and a USB cable so they're always up to date. So, with a price range of $179 to $299 you should take a look.