That, and do your power reductions starting early and using small increments. Use of the speed brakes (if you have them) for stepdowns on the nonprecision portions of approaches (e.g., FAF-MAP on a VOR approach, or initial/intermediate segments of any approach) also helps.
You mean, say, by operating them according to their handbook? Getting 375HP out of a 520 cubic inch aircraft engine whose basic design was intended for 260-285HP really is pushing the limits. That's why engines like this and the TIO-541 in the Beech Duke have comparatively short recommended TBO's and the experience is that they don't do well in making those without major work in the middle. The thing speaks for itself in that regard.
Not if it's what you need.
It is, but I agree with Henning as to comparing it to a 58 Baron -- you can't compare a 600HP nonturbocharged unpressurized 6-seat cockpit-design twin with a turbocharged, pressurized 750HP 8-seat cabin class twin. It would be like comparing a 172 with a 36 Bonanza. If you need the 421, a BE58 won't do. If a BE58 will do, then you don't need the expense of a 421 and you'll probably regret having that much airplane to deal with all the time -- much as I came to regret having the Cougar most of the time, and traded back down to a Tiger, a decision I only rarely regret.
Keep in mind, the airplane he is talking about is flying professionally (air ambulance), so it is getting flown a lot more than a typical personal GA airplane.
Two words: "Purchase price".
The MU-2 is a very special case. You won't find other turboprops of similar capability/quality/vintage at those prices.
