I have been using vue intensily over the past month and i must say it has improved dramaticly since i last used it properly in vue 6.
clouds are far better if no better than terragen 2's now
its terrain fractals i find are just as good as terragen 2's
its material editor which i have always been a fan of creates great work flow and is a lot less of a headache when it comes to models than terragen.
but the winner for me is its integration into the big cg apps.
i myself am a 3ds max user and it intergrates flawlessly with max it renders superbly with mentalray and also vray, which is a big plus for archvis artists.
its ecosystem in terms of both plants and objects buts terragens populations to shame in terms of workflow and speed.
and also its 64bit
its developed very fast unlike terragen when was its last release um like 18months ago?
just my 2 cents.