I ran it for a while with my SR-71's.
Power: It's really not that much of a power hog. If I remember corectly (sometimes I do, sometimes I don't), I believe that 1.5 amps is needed to power on, then the amp requirement drops considerably.
Sonics: Flat, Neutral, Uncolored, etc. You hear your mics and the room, nothing added or taken away.
Gain: I ran it too hot for a couple of shows, until I got it dialed in just right. If you are used to running at +24, I would suggest starting the RNP at +18 or so, just to get the "feel" of it.
Customer Service: In a word, Awesome! My first RNP had a bad clip light, that would sporadically flash on/off rapidly, for no reason. I called Mercenary (vendor), they put me in touch with Mark at FMR who is the engineer, pres., customer service rep., and just about everything else in the company (his wife does the shipping though). I spoke with him at length about the problem, he had me do a series of the usual tests (switching mic cables, gains, etc) and then told me to send it back to him and he'd get me out a new one. Sent mine back the next day and the following day there was a new RNP at my door that he 2nd Day Aired from TX to NY, based solely on good faith!
I used the new one for a few more months, but then got a deal on the Aerco that I couldn't pass up. Besides, the RNP's sound doesn't really mate that well with the EW sound, and the Aerco fits the bill nicely. Called Mark back up, explained to him the situation, he agreed to take the new one he'd just sent me back for a FULL refund (-shipping).
Enjoy your new toy! - Matt