I don't knock them and Helmut gives in one of his posts a great example where they are not just helpful but necessary.
What I tried to say (not very successful it seems) is just that a beginner shouldn't use them very much.
I told about my own experience but know of other people who really got into a dead end modeling wise because they are very tempting in the first stages of learning 3d. But they don't bring you much further.
And yes, Cheetah's booleans are quiet good, the resulting geometry is ok, but usually not a good way to create clean geometry.
Also, there are no hard and fast rules for 3D modelling. Arch Viz, stage design, engineering, human modelling, scientific concepts, 3D printing (and a few more) are far too different to be comparable.
I don't agree fully. In my opinion it has more to do with the techniques you use to model (for example subdivision), hard edge and organic types. You can create a hard edged mesh with several methods, and it doesn't seem to me, that it is very important for what you'll need it in the end. Of course, all this different types of 3d usage have their special problems and necessities. For gaming you still need relatively low poly models with normal maps, 3d printing is special, for arch viz you often have to deal with imported CAD-Models (and in the worst case have to recreate them). And so on.
But you use the same techniques for modeling in the end, have the same materials and problems with animating. So for example with human modeling it's not the modeling techniques that are difficult to learn (it's the same as with other organic forms), but the knowledge of anatomy. This is the main reason why I could never model a real photorealistic human being.
So there are a few principles in modeling that stay the same, like to understand a form to really be able to recreate it in a believable way.
Bryce still has the strongest boolean engine I know of
Well booleans have gone a long way since. There is mesh fusion (modo) and similar plugins for maya or 3ds max, and of course live booleans in zbrush. Those produce in the end geometry that is or can be subdivided (only a bit dense).
And stacking of several forms, added, cut or intersected, to get the end result is probably similar to the layers mentioned. There are possibilities to change, thicken or lessen, the edges, too. And you can group this stuff, see the results live, and in the end create a normal mesh out of it.
Stuff like this is on another level than the usual booleans; it's a modeling technique of its own.
That said, in Cheetah booleans are very mighty and well done. Don't get me wrong here.