There is a massive library of free community-made liveries available online, covering almost every airline that ever flew the NG.
Choose between different CFM56-7B engine ratings, affecting your takeoff and climb performance.
Many simmers have invested thousands of dollars in FSX-compatible hardware and scenery. For them, the iFly 737 is the perfect centerpiece. It is less resource-heavy than some of its competitors, allowing for "hot" performance (high frame rates) even on mid-range PCs.
The Flight Management Computer is the heart of the plane. iFly modeled VNAV, LNAV, and RNP approaches with precision.