Hi grrowler,
Not sure whether it is the visuals or the lack of "seat of the pants" feedback
I think it is because there is no delta g in the sim (everything feels like 1 g) and there is no sensation of heading change detected by your inner ear (sim is bolted to ground on constant heading).
The big advantage of practicing anything in the sim, is that you won't die if you
it up, giving you the chance to get the procedure correct.