I have submitted my ticket reply to e-on with quotes from this thread. I'm not posting here the whole thing becuase its a bit long but I've asked them to make the thread public so I dont have to keep up with the 'cut&paste'.
In any case, I'll update this thread with their response one way or another.

By the way, I looked more carefully at their 'best offer' of a $400 voucher I mentioned above. It said
"We offered you to return your copy of Complete and get a $400 discount on Infinite."

So from that it seems you CAN NOT keep v7complete in addition to v7 infinite. It is the same as an upgrade, you only have ONE v7 version when this is completed. So, as I said if you upgrade v6inf->v7inf you pay $400. If you upgrade v6inf->v7comp->v7inf you pay $600. Not a serious suggestion.
Chipp and Dave:
Thank you both for sharing your experience with the additional features. This is indeed helpful.
It's slightly disappointing that the features I considered most intriguing you find 'not needed' or 'useless'... I admit I dont do any animations at all so I certainly dont need the fancier features.
(In fact I wish animations was an optional module, and I wouldnt have bought it). But I might want to do animations at some point.
-Terrain control - obviousely I dont know how useful I would find it till I try. I cant use geocontrol - no version available for macs. In any case, vue is supposed to provide 'nature solutions', descent tools for creating terrain should be a central goal for e-on. I shouldnt need another program for that.
-Anti aliasing. You're probably right, I never did a systematic study of how much aa is needed, but I thinkI encountered cases I needed  more than 12. What do you set the quality slider to ?
-material control - I like the function editor very much and I'm sure I havnt made full use even of what's in v6, but I think I would like this new feature. It comes under the 'strive to do better and harder things' category.
-interface & view panes: these are features I would have sworn I dont need. One color scheme/arrangemnet is quite enough, but why would they have to chose a bad one:)
The FE has very low contrast particularly for parts which arnt selected. The little parameter lines at the side of nodes are virtualy invisible to me, even when I hover over them. Really annoying.
-Python scripting: it is already on my list of things I really should learn. I was a programmer in my 'professional' life so it should be that hard for me to learn, just not enough time in the day.
-macro recording: it is most disappointing that you find it useless. Maybe I'm particularly dumb, but I always have to do things more than once. Sometimes due to crashes sometimes becuase I changed my mind about some aspect. I used to work with a molecular graphics program which wrote a log of your operations. This log was editable and you could just rerun it after omitting/changing the parts you wanted. I miss this ability - I was hopping this is going in the right direction.
None of those justify an extra $500, that's for sure.

Thanks again to all who contributed to this thread so far!

"I paint that which comes from the imagination or from dreams, or from an unconscious drive. I photograph the things that I do not wish to paint, the things which already have an existence."
Man Ray, modernist painter
http://artpearl.redbubble.com/