I Prefer having perfectly in sync chuffs Vs what I can get with the Electronic sync......
Yes, it really just is a matter of your own cost-benefit ratio, like everything else in this hobby. If you are a stickler for perfect chuff matching at the proper driver orientation (12, 3, 6, 9 o'clock), nothing will get this right but a cam. The installation effort and maintenance effort, however, is (as has been described) quite significant. If you are less of a stickler, some of the electronic implementations (ESU, QSI) are pretty good, while others are less so (Tsunami, Econami; I haven't tried the TCS WOW! or Digitrax sound decoders).
This is part of the general question about what it is that each individual modeler considers a "must have." I have my own quirks about this - for example, my NKP GP7's and 9's have to have the protruding Mars light on the front nose, because this was such an iconic NKP "spotting" feature. But I don't much care that the horns are in the wrong place, or that it should be a 3-chime instead of a single, or that certain GP9's were Phase III's vs. Phase II's. These details that I don't care about, however, drive other folks insane. So by all means, if a cam is necessary for your blood pressure to stay normal, just like a Detail Associates dual Mars light is necessary for mine, go for it! Diversity of views and approaches to things is the lifeblood of model railroading.
John C.