I bought a Z-VI modified Pentax digital spot meter in 1992 and used it regularly, until I left it somewhere in the field in 2010. It was a marvelously accurate and simple tool. A small and elegant design, it may have lacked "features", but that meant that I didn't have to spend much time studying it (instead of my subject). The increased accuracy when using moderate b/w filters quickly became apparent in my negatives.
For my own pictures, I found that the extensive calculations people associate with the Zone System were not necessary, and that meter just gave me useful information. Even the Fred Picker "place the high value on VIII" method worked well. I never knew that I was part of a "club" based on that choice of a meter, and I'm not sure I want to be.
After I lost the Z-VI I went back to my 1978 Gossen Luna-Pro and did ok with my exposures. Then I found a Soligor spot meter at a swap meet, and had it calibrated. That works well enough but is large and clunky; an inelegant design (I have to tape the iSO dial in place) that gets the job done- although I have no affection for it.