Bwahahahahahaha!!!
I absolutely love the OTB500 but I've never owned an amp that was MORE of a one-trick pony.
It does what it does, and pretty much nothing else. If it does what you want then that's great, but don't expect versatility.
For context, I used mine almost exclusively in the context of playing classic 70s covers (Stones, Dr. Feelgood, T. Rex, etc.) and it's just bang on the money for that.
In fairness, I also remember one occasion (just one) where it sounded truly majestic with a double bass.