Since starting this thread, I've tried one that I intend soon to experiment w/ a lot more. It exceeded my expectations and really sounded awesome. However, it was difficult to A-B, because its only output is an XLR and I didn't have an adapter to feed a 1/4" plug for my other rig or to insert in an effects loop. I just drove it either directly with my FC pickup or the Send out of my Contra and the REDDI fed my Schertler Pub.
I think a simple adapter can feed a 1/4" plug using both active lines of the XLR out, if I'm right about its transformer isolating the lines at the output. In other words, connecting either to a signal return/ground shouldn't result in shorting the REDDI's output stage. I'm going to check more carefully first, though.
See the Summit thread for more comments. I know the REDDI's less user friendly and more $$, but if it sounds better, maybe it's worth it.