You can also Run if you squeeze the stick trigger while you are keying any of the Walk keys
Here is a video of some walking, climbing and running...Keep your sound on to hear the difference between walking and running:-
It is best viewed with the resolution clicked up to 1080p and then click the Full Screen icon at bottom right.
Note...It can be quite challenging to find your way back to the aircraft and I would not advise shutting down FLIGHT when you are not in visual contact with the aircraft.
I don't have FSX but I can assure you that the terrain is as good as and sometimes better than FS9 payware addons but the airports are similar to default or probably a little better and more accurate than default...You can't possibly expect this large number of airports to be as good as Aerosoft payware airports when the whole of Alaska is only £10