I think that the greatest frustration comes from the software not reaching its potential. For many, myself included, the idea of a virtual Mg modular is inspiring and exciting. Many of us like to build our own sounds and the patch cable paradigm is both familiar and flexible. Since I'll never own a real Mg modular, this is as close as I will ever get.
First, the good news. The MMV sounds great. Fat, warm, and lush. Does it sound exactly like the real thing? No. But how could it? I have no illusions on this matter. That being said, the MMV is capable of some classic synthesizer sounds and some way out stuff as well.
The bad news is that the bugs interrupt the creative flow. If I'm composing and I encounter a technical problem, I then have to go into troubleshooting mode and that has nothing to do with music. As a responsible user, I consult the manual, which almost never solves the problem. Then I scour forum after forum, which is equally fruitless. Before I know it, 30 or 40 or 60 minutes have gone by, my problem isn't solved, and and I'm nowhere near the frame of mind I was in when I was actually composing music.
I really want to use this software and get deep into it but I can't because it is too dysfunctional. I suspect that if MMV was as big a seller as Arturia's other products, there would be more support for it. It is akin to NI's Reaktor, another great app that is very slow to progress because NI is turning its attentions elsewhere.
The best I can do is cast my vote in favor of Arturia paying attention to the MMV again. I hope this happens and that I can come to rely on the MMV as a creative tool. If not, it won't be a surprise. The real surprise will be a functional V3.