What you said about instrumentals creating "imagery and landscapes" is so true, I feel the same thing. I think that's where shredders like Al Di Meola (ok, he's a jazz guy, but he can shred!), Satch, and Vai stand apart.
Anyways I feel the need to defend my hero :) (I'm being facetious; Steve's not really my hero, more like a source of inspiration). You were pretty harsh on that song! About what you said about needless speed, remember that sometimes guitarists (especially Steve) tend to do things and use techniques not simply for it's harmonic or melodic content but because it creates a sort of "sonic soundscape", where the sheer texture of the playing is more the focus then actual note choice. This can be done in a lot of ways; Steve tends to use tools such as intense speed and extreme use of the whammy to achieve these almost "non musical" elements of music. To me, the use of this type of thing can create just as much imagery as a well placed note can. Here's another example: Here at guitartricks a while back, we had this frequenter named Bofatron Sofasorus (I think his site is shredlikehell.com). Unbelievable speed. The guy developed new techniques and a whole new approach to speed, and the results were unbelievable. Parts in his compositions were so fast that they just sounded like white noise. He explained that the purpose of this "non-musical" playing was not to create pretty melodies or hooks, but to create unique textures within songs that tend take on a musical value all of their own. To really understand what I'm talking about you should probably check out some of his stuff. Anyways, point is, I think if you train your ear to recognize and understand this type of thing it becomes better appreciated.
As for the repetitive thing, well I'm not sure I'd entirely agree that repitition is always necessary to produce something pleasing to the ear, but I agree it can help. For the Love of God really follows the same theme throughout, peppered here and there by variations and punctuated with some of those "sonic soundscapes". So I don't think it's fair to say that in this song Steve is just wandering aimlessly (which I agree some of his stuff is known to do).
I agree the song is pretty extreme and hard to appreciate. It requires a time and place. Oh and don't get me wrong, I'm not infatuated with the song or anything, but I think it's a pretty solid peice of work. Really my favorite Vai song would have to be "Tender Surrender". Get the video and tell me what you think... I'm ready to defend it ;)
oh and sorry you aren't able to do the vocals for the collab thing. Maybe next time? I hope Chris doesn't ask me to make an instrumental out of the track... I'm no Steve Vai ;)