I had a whole big discussion about that over at CGTalk:
http://forums.cgsociety.org/showthread.php?t=313047
I agree that Vue promises a lot that doesn't seem to deliver upon installation - I've still held off upgrading my Vue5i to V6.
I love what Terragen 2 is doing - even at the CTP stage; being able to move out from the ground to
planet orbit is something I've aways wanted to do in my animations (and passing though a nice thick cloud layer going up or down!)
I felt Carrara was better because you can MODEL with it, loads Poser animations etc.
Unfortunately, I feel all of Eovia's great software is now left in limbo so I'm not sure what's going to happen to Carrara (figures all of this would happen after I BUY INTO it...)
Only time will tell if Carrara will continue to be a great alternative to Vue (as I felt C5 was to V5.)
-Will