To add my 2c worth, I bought an SB-400 for travel purposes. I knew the limitations so was not disappointed. I still love the pocket size simplicity. Regularly bounce it indoors but only in landscape. It also eliminates lens shadow that happens with the built-in flash at closer ranges as the hotshoe elevates it enough.
I then added the SB-700. Will add another in due course. Maybe even an SB-910 to cover more bases. Always knew it would come to that. More grunt and capabilities. Travelling around Europe from March. Would love to take the SB-700 but sanity will prevail. The SB-400 will make the final cut on packing day.