I use the "regular" Hasselblad PM-5 (?) 45 degree prism, without the exposure meter.
The 45 degree prism allows the use of a Polaroid back - the ninety degree prisms do not.
At first, viewing at 45 degrees seems awkward, but I found that I adapted to it *very* quickly.

I've been mulling over an ARAX modified, quality-ized metered prism, as, more or less a "back-up" for both the Hasselblad prism and my exposure meter. Good price, and so far, I have heard nothing but favorable comments about ARAX.

Anyone out there have any additional comments?