FlightGear 2.4 presents a brand new weather module, many graphical enhancements (support for drawing full 3D images), new cockpit systems, an experimental HLA interface layer, support for downloading new scenery "on the fly", and many other changes. There's support for more than 500 different aircraft.
The new weather module in FlightGear 2.4 sounds quite interesting and is even capable of downloading local METAR weather data to use for the weather conditions.
As a pilot myself, I prefer X-Plane from Laminar Research, but I'll be sure to give FlightGear 2.4.0 a shot when time allows. X-Plane also allows automated benchmarking in a rather nice manner.
The FlightGear 2.4.0 release announcement with download links can be found at FlightGear.org.