I use it all the time.
especially for drums. I have my drummer play, then hit calculate and it dials in pretty much the right gain for each mic injput. I dont use it on vocals or guitars since they dont seem to have such volume bursts as drums, but heck you can try it and see. I do use it on bass too. i also like it too when recording multiple songs, that way i am esured it will be consistent from song to song.
it is a little softer when you listen back, but it gives you enough head room to add eq, compression and effects that will bring the levels up as you add each of the previous mentioned things to it. If you want just a raw sound and dont plan on adding any earcandy to it, then i would suggest doing the standard mic level check on each input.
just as long as you are still achieving the tone of what you are recording, there is nothing wrong with having the levels at -15 to -10 when recording. Put on your engineeers and mastering helmet and bring the levels up slowly using your loop effects section, as well as your input patches.
just my ideas, hope this helps out. have a great weekend, i cant wait to hit the stage myself.