The points have been covered pretty well so far, but I'd take exception to the assertion that Mooneys will "bounce and yaw" more than a Cherokee... uh, no. Higher wing loading and great stability = a good ride in turbulence, at least in this class. It has nowhere near the unpleasant ride compared to many other planes. There is plenty of dihedral, and it makes for a very stable IFR platform once it is trimmed correctly.
Low drag was a major design goal, and the payoff is much greater efficiency and speed in the 180-200 hp class of planes. The cabin is indeed wider than many other popular planes, but it is shorter to save weight and drag. The seating position is more like a Corvette or Porsche, with your butt lower to the floor and your legs stretched out in front of you vs. sitting "up" on a kitchen chair. The panel is a bit closer to you compared to some other planes. You may or may not find it comfy... I do as a 6'1" guy with long legs. I've flown up to 6 hours non-stop and it works great for me. There is plenty of headroom too, so even taller folks can find it comfy. If you're >300 lbs you probably won't like it, though, especially working the fuel selector. The back seat in the intermediate and long bodies (M20F/G/J/K or M20M/R/S/TN) is also very comfy with plenty of leg room once the front seats are moved forward into a normal position. The short bodies (M20A/B/C/D/E) are cramped for all but kids, or one adult stretching out sideways a bit. (I have a couple hundred hours as a kid in the back of a C with my younger brother). The wing is indeed a laminar design with flush rivets over the forward 2/3 of it, meaning much lower drag. The down side is more exciting stall behavior compared to a Cherokee or Cessna, but this isn't a big deal at all. The entire empennage does pivot for pitch trim, so there are no excessively deflected elevators or trim tabs to increase drag.
Another Mooney feature (or quirk if you're not a Mooniac
) is the landing gear design. Mooneys sit low to the ground and have shorter landing gear than a Bonanza, for example. The suspension consists of a stack of rubber donuts instead of an oleo strut, which is longer, heavier, and more expensive but certainly more forgiving on the ground. The Mooney design is efficient in all aspects, but gives a bouncy ride on the ground and is much less tolerant of poor landing technique.
Getting 16-18 NMPG is routine for me in my J, flying at 145-150 KTAS LOP. I have ~1020 lbs useful load that lets me carry 4 non-obese adults + bags 500 NM with IFR reserves in 3.5 hours or less. There are few planes that can do that without burning a lot more fuel.
