Like mentioned above, it can be a bit of a stiff ride in a head sea, and the motors are extremely expensive to rebuild. I like the way the MANS Run but the maintenance is expensive. Like the difference between maintaining a car engine and a race car engine. That being said I Love the rest of the design. Huge aft deck, wide walk around decks, a small cockpit to fun fish, swim or dive from, and no ladders to climb on the whole boat. I know multiple levels can be an issue for some people but to have no ladders and only steps is great for older people, and kids alike. Tie all that in with a fast riding, convertible style, shallow draft hull, and you have the Perfect South FL, Bahamas/Keys Cruising boat, which is where we spend all our time. I would look for the 1050 or 1200HP powered optioned boat though before the 820. Maybe easier to resale.
You mentioned what else is out there? One of the members has a 1998 Hatteras 52 MY listed under boats for sale with CAT Power. I'd have that on the top of my list if I was looking for a 50-60 ft Motoryacht. Or like you mentioned don't be afraid of a Hatteras 54-65 Convertible. A 65 Convertible is a Great cruising boat that is at the top of the food chain when you talk about quality, solid ride and just in general a hell of a sea boat. It will run in nasty conditions with the best of any other Sportfish/Convertible boat ever produced. They will suck up a lot of fuel also if you run them hard, "BUT", if you run it at slower speeds it's every bit as efficient as a big Motoryacht. I personally Lean toward Convertibles because they give you the best of both worlds, Luxury accommodations of a motoryacht, but with speed and the BEST of sea keeping ability of any type of pleasure craft available.
When I grow up one day, my dream boat would be a 4 Stateroom 1997-1999 CAT Powered Hatteras 65 Convertible. The 70 Convertible is nice also, but a deeper draft, and well, there's just something about the look of the 65 that I really like. I can't put my finger on it, maybe the low cockpit freeboard and stepped sheer, or the shape of the boat house and bridge without all the round flowing curves of modern boats, I'm not sure. It just looks like a "Man's" boat, a man's boat that is just soft enough to appeal to women as well. It's a perfect balance of a low cockpit, and balanced house and bow length. The boat has a an elegant, handsome, yet chiseled look to it. A look that anyone walking the dock doesn't have to question it's purpose or it's capabilities. Again I can't put my finger on it but who ever drew up the final exterior design nailed it. That 65 will never look dated or out of place in any line up, in any marina, anywhere. It's like the Marlboro Man of boats.
Tony