I am one of those good reviews of Octave as well. I use it sometimes for feedback frequency identification between the 1/3 oct bands. Works great, and the new features definitely come through periodically.
I'm another +1 for Octave. I have it on my phone for simple frequency ID too, which is handy for a visual reference when working quickly with things like a Lectern mic etc. After I get the show rolling, I typically have it open on my iPad somewhere near the console, again for a quick visual reference.
The handy thing about Octave is that once you open it, if you tap the screen on the main display, it will bring up a bar across the top that gives you a numeric read out of the dominant frequency. I've tried almost all of the other reasonably priced apps for RTA uses, including another one that cost like $50 at the time... Octave is the only one that earned a permanent spot on my devices.
Steve