It is a not well known fact but (at least since Vista) Windows considers RAM as a cache for the HD; this means that the more RAM it has, the more stuff it can keep available without hitting the disk, including whole programs. At very least, if you relaunch the program it comes up quicker.

In general you can have many applications open (e.g. you would have no problem in having Poser, Vue and Blender open, each with exacting content loaded) and, at the same time, handle much more data.

When I design my next computer (custom assembled since late 1990's) I always specify as much RAM as the mainboard can handle while I never go for the latest generation CPU or graphic card.

GIMP 2.7.4, Inkscape 0.48, Genetica 3.6 Basic, FilterForge 3 Professional, Blender 2.61, SketchUp 8, PoserPro 2012, Vue 10 Infinite, World Machine 2.3, GeoControl 2