I never flew the "classic" but the autostart system on the-8 works fine. As did the one on the -400. Did exactly what it said on the tin.
To be honest, in 10 years flying the Jumbo and far too long flying other Boeing and Airbus products, I never had any problems with the motors. But then I have always had GE's hanging off the wings. The only donk I ever saw problems with was made by RR/BMW. And that wasn't a very serious one.
Just my own personal experience. The BA777/Quantas A380 crews may feel somewhat different.
The fuel burn with the Gnex is pretty good although that may have something to do with the new wing as well.