I think you hit the nail on the head when you mention it was time consuming. This, I think, is the biggest reason I haven't tried my own zim yet. I have a number of different zimmerit tools including Tamiya's rakes, and Lion Roar's different roller sets. I even have the various putties to try out zimming a model. (zimming.....is that even a word?) It just adds more overall time to the build, and right now I'd rather build, and move on.
At the beginning of summer, I realized that my stash is soooo big, that at the then production rate of less that 3 models a year, I would never put a dent in it. So, I started bringing kits to my job, and working on them in the morning, and at lunch. I have completed 11 models, and have 9 more pretty much built and waiting for paint, since the start of summer. I don't think I'm sacraficing quality in these builds by doing them so quick, but that is best left up to others to decide.
I'm not saying I will never try doing my own zimmerit, quite the contrary, as I would like to give it a shot someday. But for now, I try and make my life a bit easier by adding as little to the kit as I can get away with, and still have a decent, relatively quick build.
I hope this doesn't come across as being defensive, I am just explaining my point of view.
Nate