Yes I do have mine (both the original cheap one at the time and my current CT Midi) inside my enclosure, I padded the inside of the compartment with sound dampening foam, but also made sure to have a large (4") hole at one side for fresh air intake and a large hole on the opposite side with a small air extractor (picture in that thread). I wired the air extractor such that it turns on whenever the vac is working.
That is the naive way to do this though, some of the sound will (obviously) leak through those air holes, and the right way to do this is to build the air intake such that the air follows a non-straight path (labyrinth like) to the inside of the enclosure, to break the propagation of sound. I was too lazy to do it, but for an apartment I would definitely look into building a fancy sound-reduction enclosure for both the machine and the vac.