I've used it in selfbows, trilams, and glass bows. I have a bunch of rough sawn mulberry boards. I bought them because the guy said they were osage. They had been in a barn for over 20 years, so they were really dark and dirty. Sort of looked like osage from the outside, hard to tell in a dusty old barn... but as soon as I started moving them, I noticed they felt too light weight for osage. I scraped down into a few with my knife. I told him I didn't think it was osage, maybe mulberry or black locust. He still insisted it was osage. Then I wasn't sure, but the price was good either way and figured I'd use it no matter which of the three it was, so I brought it home. It was obvious it wasn't osage once it was standing next to some equally old osage boards I had... and as soon as I cut into it. Osage? No friggin way.
Now, was it mulberry or locust? Seemed a little bit light weight for locust too, and it failed the black light test. Black locust glows like it's radioactive under a black light, mulberry doesn't at all, and there was none of that, so I'm confident it's mulberry.
No, mulberry isn't 'bad', but it isn't osage either. I sure wish it was osage. It was about half a pickup load of boards about 10' long. Oh well, live and learn.