The full Terragen 3 product line is now officially available, starting at $199 for Terragen 3 Creative. Details on the wealth of new features, example images, video tutorials, and more over at Planetside.co.uk: http://planetside.co.uk/new-in-tg3
Planetside Software has announced a major new version of Terragen for release in July. Terragen 3 Professional is aimed at the visual effects market and other commercial users, but there will be a new "Creative" version at a lower price too. More details, example images and ongoing news up
Xfrog has released a good number of sample models from their plant libraries for free download. All in all, there's supposed to be some 130 different models. I have counted 30 different plant species, with each one coming in multiple models.