Features include:

Ultra-Flexible Sidechain Routings
Apart from excellent sound, FabFilter Pro-G also provides very flexible routing. You can choose between mono, stereo or mid/side processing and in expert mode, external side chain input is available with completely customizable channel linking and routing.

Clear and Precise Metering
FabFilter Pro-G combines smart input/output level meters with a real-time level display and transfer curve. Everything was specifically designed to give clear feedback on the current gate/expander settings and processing, letting you set them up easily.

FabFilter Goodies
Of course, you also get all the usual FabFilter goodies: perfectly tuned knobs, MIDI Learn, Smart Parameter Interpolation for smooth parameter transitions, an excellent help file with interactive help hints, SSE optimization and much more.