I'm reminded that Frank Zappa recorded every concert he ever played and used to strip the recordings back to basic rhythmn section then start to rerecord over the live tracks. His reasoning was that the energy of the live show brought out the best in his drummers and bass players and gave his songs and tunes tremendous vitality. In the studio he would also put a mic in front of his electric guitar to pick up string squeaks, pick noise and overall handling noises which give his playing greater presence and dynamics. I always keep room mics running in the studio to mix in to whatever I'm recording. Sometimes its appropriate, sometimes not. As the guy who taught me much about sound recording said. 'If you havn't got it, you can't delete it'.