I went to the Double Door for the first time in 2001 when I first moved to Charlotte. Ten years later I still love to drop in on the occasional Monday night to have a beer and groove to the Monday Night All Stars - their long standing house band. You will not be disappointed if you like rhythm and blues and old soulful tunes.
I've honestly never been on a day other than Monday so I cannot comment on what other live music acts are like on those nights, but I know that Double Door has been around since 1973 and many great musicians have come through there.
My favorite part about the Double Door is the variety of people there is to mingle with - it's 100% real and zero pretense - it's impossible for anyone not to kick back and get loose here.