I used top play LOTS of bluegrass upright bass. I help to put on a rather large festival here in my hometown. The sound company we've been working with showed up with these mics about 2 years back. They were primarily used for the instruments, mandolin, banjo, guitar and bass.
I was quite used to my pickup signal to a GK combo and micing the amp with a Shure Beta 52. Now, before you think that setup is crazy, I got quite a few compliments on this sound over the years I used it, from bass players listening out front.
Anyway, sound man wanted me to be a guinea pig for a bit. I played my bass over the mic with no pickup at all and the sound out front was pretty good. I had the mic placed above the treble F hole, in the shoulder region, between my right hand and the f hole. My son listened out front (this was all before the music had started for the day and after the PA had cranked) and he liked the sound.
As the first day started, the sound man tried to use these mics for all the instruments on all the bands. But as the day wore on, they kept having problems being able to hear themselves in the monitors, partly due to this mics inability to reject sounds from the rear side.
The next day, the sound company had moved back to Shure Beta 87's, due to their superior ability to reject these same sounds from the monitors.
I think the Audio Technica ATM450 would be a great addition to a small home studio for recording, but I won't be investing in one to play live through, if monitors are involved.