I STILL use Vistapro plus an old copy of photopaint3 (old-style flow fill feature, without the use of masks) to custom sculpt terrains for use in Bryce. This combo gives me the best control over all the details I want in the terrain. Once I have the features sculpted and fractalized in Vistapro (still one of the best there is for that particular function) I pull it into Bryce and do the final erosion, slope noise, etc. tweaking. Using multiple terrains for a single scene is the way to go, you can then texture/control each feature separately.