For me, the FNPTII (or I suspect any simulator) was/is, barring perhaps 10-15 of familiarisation, not much help at all. I suspect it is horses for courses, but multi engine, tracking beacons, procedural approaches and holds do not warrant 50 hrs of training. My problem was the constant buggeration factor from ATC and traffic in the now very busy regional airports and surrounding airspace used for the IR. More often than not I would not fly the filed plan. This unpredictability induced a high workload, was never really replicated in sim sessions and, for me, was the cause of my problems. Also, the asymmetric stuff in a sim is a bit of a joke really.
In all seriousness, once you know what you are meant to be doing, you can probably get the same training benefit from mentally flying in a comfy chair.
I'm not an instructor and in the scale of things, very inexperienced, but purely with personal hindsight, barring say 10 hours or so, I suspect it would be better to fly around in an Archer than a sim.