I was using the usb connection to record on Audacity.  The guitar I was using was a Fender Strat with noiseless pups.  I found that the signal stregth was really low and the only way I could get a decent recorded signal was to turn up the master volume to an unbearable level and was close to getting a stern talking to from my better half.  I then tried the same process but used some headphones and this sorted the level issue so it recorded a strong signal.  There was still a bit of crackle on the recording but much improved from the last firmware release.  

I then recorded some acoustic guitar without headphones.  This was a martin DRs1 with a stock fishman pup.  Signal strength was really good and the quality was great.  No hum or hiss or crackle.

Great to hear others experiences.