I was using flats on my Ric for some time and really enjoying the tone, and I'm mainly a stoner rock / late-80s thrash kind of guy. My wife is currently running active bass w/ flats -> VT Bass -> Carvin BX1200 in a "rock with lots of dynamic range" band and her tone is, frankly, awesome.
You'll have to adjust your EQ and your playing style somewhat to get the best out of them, but flats can sound very good in a lot of situations.
You'll have to adjust your EQ and your playing style somewhat to get the best out of them, but flats can sound very good in a lot of situations.