I have an RNLA, have used it for drums and nylon and steel string guitars (RNP, tlm-103, AT825 Stereo mic, AKG C451eb).
Most noticable on guitar is the character the RNLA adds to a track. On guitar, I a/b-ed the RNC and RNLA, and the difference is significant. There is a sublte and tasty eq going on through the RNLA that is absent from the RNC. Guitar was noticably less boomy in the low end through the TLM-103, which I've never really liked on steel stringed acoustic guitar. But through the RNLA, a new world opened up - a point and shoot world. The same thing happened with
the AKG C451eb (my model is old, not the reissue. It's an outstanding mic). The AKG has a 75khz and 150 khz roll off. It was set at 75. Through the RNP/RNLA the sound was beautiful. It's one of those pieces of gear that I can see myself using constantly because I like the color right out of the chute. Side by side to the RNC, one really gathers a picture of the rhetoric: clean vs. color. It's all true. I'm a color guy, so my poor RNC's younger brother is quickly turning into my favorite. Although the RNC would be the hands down winner when clean is the goal.
I've only used it for a few hours, but, man, it's sweet. It's one of those pieces you plug in and immediately understand what it's adding - which is to say the color is significant. But that's one pretty color, boy.