Of course I'm not a real pilot, so I can only say what I believe from comparing it to other airline sims that I have.  It is a pleasure to fly.  The flight dynamics seem to be very realistic.
I turn off the AP approaching on short final and the CptSim Block F 757-200 handles like a dream.
It is very smooth with great frame rates.  
Maybe tonight if I get a chance, I will make a landing at my Mega London Heathrow Airport.  That is a pretty intensive scenery.
From the videos I have of the 757, it seems to handle good in reality too so I suppose the good handling of CptSim's realistic.  I would love to hear the opinion of a real 757 pilot.