It's a faithful representation of the real MD80, and has been clearly programmed with great care for performances. In fact, you can compare the fps with the default FSX 737.
Is so good, that we are also working with Flight1 with an italian translation of the interactive tutorial (we did it for the old version), that will probably come out in time for the CD version.
Highly recommended: it's the living proof that it IS possible to create a complex airliner in FSX without killing its performances.