I agree that in many ways, having a practice session can be very good if you have never operated one of these machines before, but I think that there are many pitfalls to be aware of that can possibly negate the benefits. The different SOP's, as alluded to by Scroggs, is one of the key factors. I declared my practice session as I was asked directly if I had ever flown a jet sim before and didn't want to lie, but I believe this created a certain impression of me with the assessor, and not a favourable one at that.
Interestingly, in my 2 hour practice session, there was a very marked learning curve from my first attempt at a departure and landing, compared to my last one. I was all over the place to start with and was so far behind the aircraft it was unbelievable. My last attempt was pretty much there or thereabouts, with no major cock ups. In the actual sim check there was hardly any learning curve at all as each attempt contained minor errors, and correcting one error usually resulted in another minor error elsewhere. So although there were no major areas of concern per se (and in my humble opinion), I didn't demonstrate such a marked learning curve as I had done in my practice session. Something you might want to consider.
NH