Mudbox needs it.
If you have a model with lots of meshes.. (especially on a lower end laptop, intel core duo 2.4, 3 gb ram, vista 32bit. -_-) Its a pain in the ass to have a steady framerate.
With Layer editors ala Maya you can at least hide a bunch of stuff in one click. It will also make your files allot more organized. (Import from Maya to Mudbox would be awesome as well) Mudbox doesn't even allow you to group objects. If we could do that it would have been allot easier as well.
So yeah.. Mudbox needs grouping/ layers like Maya. In my opinion.
Fatih
Ps. Please excuse the typo "Confrim".