So far my opinion is still on hold until a final version. I do like the realtime 3D preview of the scene. Very slick and fast. Some things do seem a bit unrefined and unoptimized. For example, the renderer seems extremely slow in comparision to comparable rendering engines and enabling antialiased node links seems to really slowdown the node editor to a crawl. The clouds do render amazing and the lighting is very realistic, the node editor reminds me a lot of blenders oops schematic view. Some of the functionality I would think would be neat to see in Blender. ie. changing groups in oops or outliner, changing where materials link in oops.
The download page is located here.
Some pretty nice animations can be seen at the download site as well. I'd recommend downloading the documentation. Planetside also states that Terragen 2 is compatible with XFROG plants. Make sure to check out greenworks for more info on that. It would be interesting if XFROG nodes remained intact and could be animated in Terragen.