You can't use wonderboard to replace sheetrock because you can't paint it (unless you like the look of painted cinder block) and you cant hide the seams unless you use thinset. You could replace with either the green sheetrock (good) or the alternative to wonderboard they sell that has a much smoother finish which I think is called utilicrete (don't quote me, but it is sold at HD and is not cementious but has the same qualities as wonderboard relative to water).

If you are doing a tile surround, yeah, use wonderboard obviously. I did have an architect friend that used untaped, unpainted wonderboard to trim out his garage as a project, and it looks like a prison.