We bought a 30 hp CUT last year with a 72" MMM. We already had a commercial ZTR (but only a 44" deck, which is way too small for our property - we have about 4 or 5 acres to mow.)
The problem here is putting the mower on (and taking the FEL off) - since I have been doing alot of projects (new 600' driveway, new polebarn, landscaping, etc.) the FEL is usually on and sometimes the backhoe as well. It only takes about 10 minutes or so to put on the mower and take the FEL off - but I'm working on my projects so much (12+ hours a day, 7 days a week) that I find I just don't have the energy to screw around with swapping things out just to the mow the dang grass. In fact, I don't even have the steam to mow - either my wife, son, or the neighbor kid mows (every few weeks) .... otherwise it ain't gonna get done.
The idea of having piece of equipment (CUT) to accomplish all tasks was a nice one but in hindsight at this point I wish I had spent the money for the MMM on a good ZTR with a large deck.
It could be that once I get all the projects done around here that opinion might change .... but that seems awfully far down the road at this point - at least 3 or 4 years. FWIW.