GGrewve generated output for the first time today. The dictionary right now is very small and the subdivision rules are very strict, so there's really no variety in the drumming yet, but that was intentional so that I could test the engine. Everything worked very nicely.
One of the cooler parts of the engine is the "humanization" function that varies the velocities to simulate a "groove" as well as add ghost notes to the snare drum like professional drummers do automatically. Even with a tiny dictionary (right now it has only five simple words that correspond to four-beat patterns) the drumming quality already surpasses the Variating Drummer, so I think I'm on the right track with this plugin.
I've still got obstacles to conquer. Most notably, I have to devise a way for GGrewve to determine which words are "fancier" and "heavier," so that it knows in what context to use the words. For example, a fill should obviously not come on the first beat of the first measure of a section...it should be saved for a turning point or a transition into another section. I could just include some quantitative specifications in the word files to let GGrewve know where they should be used, but I think that's taking too much of the computer work out of it. I'll write the words but GGrewve has to figure out how to use them. This will, of course, be a lot more work that just telling it when to use words, but I think the results will be more satisfying. Expanding the dictionary will also be a lot easier if I don't have to take the time to think about when each word should be used.
In conclusion, I'm excited about where the drumming side of mGen is going and I think GGrewve has a bright future.