Yeah, it's strange Ted. The tone goes all buzzy and flabby. On the other hand, my Laney Klipps love the BoR but they stay pretty clean up to half volume.
I think the trouble with some pedals is that they work best with a clean or very nearly clean tone. The Little Rock has crunch even at low gain settings on the clean settings so a pedal that needs a really clean tone sounds pretty pants.
The Tubescreamer works really well though, and my Marshall Guv'nor wasn't actually that bad either (if a little fizzy). I'm finding I'm using the Clean setting more than the Drive, as it just sounds sooooooooo good!