I've finally started to delve a bit into digital painting using Corel Painter IX and Adobe Photoshop. The investment also includes a Wacom tablet and a bunch of training DVDs from The Gnomon Workshop, which are excellent. What is particularly interesting is that on my first try, which was admittedly not of a very challenging subject, I banged out a painting in a fraction of the time it would take to use traditional media. One knows of this potential going in, but to actually do it is another thing entirely. 
Digital Paintings
First Digital Painting
VSS Enterprise
FAA Cover Concept
Suborbital Sunrise
2011 COMSTAC Forecast Cover
Dude on Mars
Asteroid Miners
MPCV at the Moon
MPCV at Mars
NASA Space Launch System
Mercury
Centauri
Venus