So far it seems that BlogRush is pretty much useless. I can't see how it has added any traffic to any of my sites - actually, it's more likely to take away traffic since it's another exit point.
At this point, I'm not even sure I understand why I should be using it - since it has generated little or no traffic to any of my sites, and the benefit of accumulating the BlogRush credits is unclear to me at this time, I see no point in devoting any of my sites' real estate to the latest widget. I suppose that one must promote BlogRush in order to truly benefit, and if that's the case, then it speaks volumes about the program.
So... I'm removing it from all my sites for now. I'll check it out later and see if it's worth using.