I'll try and answer your questions, but you'll have to understand that it's been 15 years since I've flown the MU
-2 - so if make any memory induced errors I'll have to leave it to others to correct them.
One of the design criteria for the MU
-2 was to design an airplane that would out perform its competition - the various King Airs, Turbo Commanders and Merlyns. At the time, Cessna and Piper hadn't come out with their competing aircraft yet. The Mitsubishi designers actually came up with a pretty good way of accomplishing their goals - they used a relatively small, high speed wing (it's about the same size as the wing on a Cessna 182). To allow the airplane to operate out of shorter runways they used full-span fowler flaps. To provide roll control in conjuction with the full-span flaps, they used spoilers for roll control. All in all, it's a very effective way of doing things especially when you think that the design was done back in the mid-60's. That's the good news, the bad news is that the airplane, because of the spoilers, had a very "quirky" (read: different) feel to it when it came to the roll axis.
The wing, as I mentioned, was comparatively small and there wasn't a lot of room, internally, for fuel so tip tanks were added. This resulted in a lot of weight out the wing tips - which added to the distinctive feel of the airplane. You Lear pilots will understand the feeling very well, you guys who fly Cessna 310s and 340's will have an idea of what it's like having all of that weight out on the wing tips.
As far as the spoilers go, they aren't very large, as I remember, they are about the same size as a standard yard stick. They are effective enough, not there's no "feel" associated with their use - artificial feel is provided by springs attached to the spoiler linkages. The resistance that they provide is the same regardless of aircraft speed. The spoilers are effective, but their effectiveness is a function of aircraft speed. At low speeds, it takes a whole lot of control movement to get a response. It's not dangerous, just different. At high speed, it doesn't take very much movement to get the desired result. Again, it's not dangerous at all, just different. In fact, since the airplane uses spoilers (lift destroyers) for roll control instead of ailerons there is no adverse aileron yaw and therefore little or no need to use the rudder in turns. You can roll the airplane back and forth with your feet flat on the floor and the ball will stay square in the middle of the turn coordinator. Roll trim is provided by small "trim ailerons" which are actually small trim tabs mounted on the trailing edge of each flap.
Now for the "Jet like" characteristics. As I said in a previous post, the MU
-2's wing loading is comparable to the Lear 35, T-38, and Boeing 727. The airplane needs to be flown fast to get the lift from the wings. In standard propeller twins, in the event of an engine loss, the drill is to clean up the airplane - retract the gear and flaps - and accelerate to "blue line" (best single-engine rate of climb speed). In many twins, you're only looking at having to accelerate a few knots to get to "blue line". The MU
-2 is a totally different breed of cat in this area. Because of the small, highly loaded wing, the best single-engine rate of climb speed is 156 knots. (Based upon flaps O) The takeoff flap setting is Flaps 20. Vmc is 99 knots. If you suffer an engine failure right at rotation - or shortly afterward - the normal response of a "normal" light-twin pilot is to clean up the flaps and "go for blue line". This is the correct response for nearly all propeller-driven light twin aircraft that I can think of EXCEPT for the MU
-2. Under those conditions, you are nearly 50 knots below the best single engine rate of climb speed and you just pulled the flaps out from under yourself. The airplane is going to do exactly what airplanes do under those conditions - turn itself into a lawn dart. The MU
-2 procedure is basically the same as it is in many jet aircraft. You maintain your current configuration and wait for the aircraft to accelerate. As the airplane accelerates, you perform a progressive clean up - you don't fully retract the takeoff flaps until you've accelerated to 156 knots. When flown properly, it really performs well. When flown like a King Air or Seneca, it will kill you every time. Pilots with jet time have no problem with the concept, pilots without jet time need to be very careful. That's why simulator training is so important in high performance aircraft like the MU
In the real world, it takes most guys around 50 hours or so to get comfortable flying the MU
-2, about the same as it takes most guys to get comfortable in a new jet. The MU
-2 is a very well built airframe, to my knowledge, there has never been an AD
issued against the basic airframe. It is quirky, but that's what makes it enjoyable to fly. It's one of those aircraft (like the Lear) that you have to be awake when you fly it and you have to work at to give the passengers a good ride. It's been said that if you can fly an MU
-2 (or Lear) well, you can fly anything well. Personally, I'm glad that I had the opportunity to fly them. I think that the experience make me a better pilot.
Oh, by the way, I've noticed that the majority of those pilots who bad mouth the MU
-2 are pilots who have little, if any, actual time flying the airplane - kind of like the old Luscombe storys you used to hear about. (I owned one of those too and it wasn't anywhere near as bad as the hangar experts would lead you to believe.)