I've heard about the Ruby scripting, my friend who uses it says he's got Summoning and side battle systems running - which I suppose makes it useful, but it could do with a bit more evolving in game play terms - graphically it's better, now with hi-res sprites and VX has an improved sprite system and I'm sure the scripting system makes it more customizable.
But, RPGM 2003 still get kicks out of me and is good for visualizing my projects when I actually get the bloody time to code them.
"Experience never provides its judgments with true or strict universality; but only (through induction) with assumed and comparative universality." - Immanuel Kant