I had a funny "story" written for this but then my wife accidentally deleted it. It started with, "Once in a land long ago there lived a Prince named Edward..." Oh well. Here's the generic version...
EVH in about '89 went to Music Man (I'm not exactly sure what brought the two together) and worked with them to design his first truly signature guitar. He designed the body and I specifically remember reading an article where he said he "wanted to get away from the whole Strat thing" as far as the body was concerned.
The neck was an exact digital reproduction of the neck on his famous red and white 5150 guitar used from '84 on. It was a reproduction right down to the wear EVH had put on it through the years of touring and studio work. This guitar was in production for roughly 6 years and they produced about 1,000 of them each year.
EVH left Music Man in '95 or '96 to go to PV. At that time the Music Man EVH was discontinued but after a few months of retooling it was reissued as the Axis. Changes to the EVH that eventually made it the Axis were:
-The neck/fretboard is slightly wider at the base
-Pickup switch was moved from up by the neck pickup to down by the volume knob.
-The rear route for the pot cavity was made big enough for two pots and a switch where the route on the EVH was only big enough for one pot.
-A rear body contour was added to the Axis
-Various versions of the Axis were offered with different pickup and bridge configurations.
-They produce more than 1,000 each year now
The rest of the Axis is the same.
Why did Ed go to PV? That depends on which web board you post the question on. The official line from Ed is that he wanted to make changes to the guitar and going to PV was the only way he could have those changes made. (This is where the loyalists here will start replying with great disagreement...

)
The Axis is very similar to the EVH especially since the pickups are the same. I've heard people say that Axis don't come close to what the EVH's tone was. Honestly, I've not played enough of the Axis' to make that observtion. I've played one that was great and I've played one that I thought was fairly dead.
I own an EVH and am quite happy with it. It's a great guitar.
Hope this answers some of your question.
And let's not get too carried away with the PV insults o.k....
