Hi Grumbleguts,
Generally, when folks are referring to "Virtuals," they're referring to pictures altered with photo editing software like PhotoShop or Gimp.
There are Virtual Bonsai programs out there (JFP made one) but they don't do much for the purposes of bonsai design (that said, I'm sure there is someone out there who can do wonders with them).
There are also, like you mentioned, several tree rendering macros and plug-ins available for different modeling platforms but I don't see many folks around here using them. Most just stick to what is quick, efficient (photo editors, sketchbook) and gives them what they need: an idea of how to proceed.
Right now I'm playing around with L-Studio, a 3-d modeling software developed by the University of Calgary's Computer Science Department for the study of Algorithmic botany.
It's wayyyyyyyyyyyyyyyyyyyyyyyy deeper technically than any bonsaiist would need, but fascinating in that you can model the specifics of individual cultivar's growth habits as well observe them interacting with accurate virtual environments with an absurdly high degree of specificity. Since it was designed for creating scientifically credible growth models it's more statistical botany and computer science than artist sketchbook, and the learning curve isn't just steep, it's Everest. Absolutely not recommended for virtuals but nonetheless interesting.
There are lots of folks here who are experts with PS and Gimp (I’m not but I can get by) and if you’re looking for assistance they can help you along. If you’re already using POVRAY chances are you’re already technologically savvy but here’s a PS primer for virts:
http://www.artofbonsai.org/tutorials/photoshop_virt.php
Later propagator,
- JDW