PS CS3. The ultima ratio for image editing, if you ask me.
I started with Paint (geez, that was long ago), went on to The GIMP, continued with PhotoImpact and ended up getting PS.
Really, anything else is an imposition after you worked with PS...
Colonel Jade, your version is nice, although the style certainly differs from mine. I prefer very clean and minimalistic signatures, containing only the most necessary.
Constructive criticism: I'd move the Osiris and the RT more to the left, getting a nice composition following the rule of thirds (sorry, I'm a photographer).
As well, the fonts are not really matching - either go for the Star Wars one or take the curly handwriting font. I like the clouds and the planet in the background, although that horizontal line is a bit disturbing. Overall good work:)