The SIM itself is not difficult, no abnormals or emergencies. On the paper its indeed quite straightforward.
But they can make it a hell.
No AP, no flight director, no autothrottle. Do not plan on any help from your PNF: he is not going to do almost anything. He will not even call for positive rate, for the minima, etc. He will answer to the radio, but he will not even change the frequency if you dont tell him to do so.
I was in HAM, out of runway 23. North departure, based on 2 NDB.
Variometric climbs and descents, steep turns, then direct to a VOR for the holding (figure out the entry in less than 10 seconds, and expect climbs and descents in the meanwhile), one round with relative wind corrections, and other climbs/descents. 3 vectors and you are already on final ready for the ILS, hand over the controls to the PNF, but be ready to take it back when instructed to climb or descent or turn: he will only keep the plane level. Set up the frequency and do a briefing in less than 45 seconds. I was vectored at 9 miles, glide already in when on the loc, but still ok.
Go around at about 30/40 feet AGL, standard missed approach, and again after no more than 15 miles I was already on final for an NDB 23.
Good visibility, normal landing.
I was quite rusty at the beginning, I really improved a lot during the session, but I wasn't precise enough during the navigation in their opinion. I admit the departure was not really good, but I noticed the mistake and recovered. Overall I was pretty happy, but it wasnt enough for them. Congratulations to the people not rated who passed: you have all my respect.
If you have a decent experience on the 737 it would be easy enough I would say. For a non rated... its not easy, really, even if you have jet experience, like myself.
They will push you to the limits, overloading you. And when you begin to fell a little more comfortable, expect some extra pressure, again and again.
Good luck!