I have the AE Prism VF and it is consistently inaccurate so if you get one make sure and test it. I love this camera (mine is the SQ-A) and I love shooting in 6x6. I also have the 645 back for it but rarely use it since I have an ETRs for that. I have the 50mm, 80mm and 150mm (all are the older S series). I especially enjoy using it hand held and believe that the leaf shutter Bronicas are some of the best for handheld medium format. Therefore I regularly use the speed grip.
Of course I love my RB Pro SD too but that's another story.