My current partner's Mars is conj my Pluto, and my Pluto is exactly trine my Venus in my natal chart. So it's a Venus/Mars and Pluto/Mars thing combined.
He is the best sexual partner I've ever had. There is strong passion and love between us in a way I've never had with anyone before, yet it feels completely normal and comfortable. Our relationship is also highly charged, in that sense that we energize each other simply by being around one another. Even if we're just sitting around watching a movie, we can easily stay up all hours of the night and not get tired. I attribute this to Mars/Pluto but I'm not totally sure.
The conflicts we've had have been very intense. Not abusive or anything. I just mean, if we ever turn oppositional because we don't understand one another, the energy of that opposition is intense. It hits me right in my body and I start shaking.
I would say that Mars/Pluto is neither good nor bad, but that it depends on how you work with the energy, as well as the other aspects in the synastry. My partner and I have a lot of positive growth with one another, but that's because our charts are relatively harmonious. I would not want to be in a Mars/Pluto relationship with someone if our charts had a lot more hard aspects. It would be hell and I could see how that energy could turn violent.