The -200 was a fun airplane to fly but when they created the -300/400, not so much. Too much fuel and too slow for the long legs. Droning across America headed for the west coast at 0.74M? In that small cockpit? Not fun.
Didn't fly the NGs but when Herb got Boeing to build him some baby-757s with a new wing, more thrust, higher ceiling, more speed, it was a stroke of genius. same type rating but not the same airplane.
Also, speed brakes not very effective and combined with the typically slow extending flaps/slats, it is not an easy machine to get slow or down.
Reliable? Yes. Easy to fly? Yes. Comfortable cockpit? Not really. Suffice it to say, not my favorite although I flew it for more than 15yrs.