Sorry for the delay in replying Buzzzzz, we've all been a bit busy with various things. I'll be going through all the messages over the next few days and replying.
In any case the built-in erosion is definitely an in-progress feature. I would say all the heightfield modifying nodes are, in fact, and I tend not to use them. You're generally better off creating any heightfield terrains in a separate app as you'll get more control and stability. TG2 doesn't yet offer many particularly unique heightfield functions either. All this will be improved for the final release, of course.
But if you do want to use the heightfield effects one major thing to keep in mind is that both the built-in heightfields and certain effects (such as erosion or river) must be *re-generated every time you close and re-load the file*, unless you save the result of the heightfield after generating/editing with Right-click and Save Terrain As (on the heightfield node). This is because TG2 saves only the descriptor files (.tgd) which are very small but do not contain the actual heightfield raster (pixel) data which would be much larger. Saving the results of your heightfield editing can be done as above and then simply replace your heightfield generation and edit nodes with a heightfield load.
Imported terrains, from WM or otherwise, certainly shouldn't be losing detail. In fact TG2 adds procedural detail to heightfields by default. You may want to turn this off if your heightfield isn't looking the way you want it to. Go to your Heightfield Shader on the Fractal Detail tab and uncheck Add Fractal Detail. However it's not likely this is causing your problem. One thing I know are an issue with WM terrains in particular are height values and scaling. WM has had an issue even with TG 0.9 and outputting incorrect heights to the .ter file. You can use a Heightfield Adjust Vertical node in TG2 to get the correct scale or just adjust it in TG 0.9 and re-save with correct values.
If you're still having problems with imported heightfields after trying these things it would help to post some example images - perhaps one of the heightfield in WM or TG 0.9 (the way you expect it to look) and then one in TG2, pointing out what's wrong.
- Oshyan