Sorry, but I stuffed up the voting thing. I thought that pushing the button would take me to a separate voting screen, so you need to remove one vote from the first question.
Turning to matters of substance, I have an SB-900 and two SB-600s. I plan to acquire one or two more units, either several used 800s or a new or used SB-900 so that I can further explore the whole lighting experience. Given that I am an amateur whose photographic interested have not yet coalesced, I cannot imagine that it would be cost effective to go down the radio route in the forseeable future. I think I would be better off spending money on some stands and light shaping tools. If I was a professional photographer, and if it represented a good investment for my type of photography, then I would go radio. The proviso is that I would need to be absolutely certain that it would work reliably. Based on what I read on this Forum, I am not certain that I would make the investment yet.