I am a Detroit dude, so I've seen them many times and hung out with them, my friends' bands have shared shows with them, etc. At shows, they are all pretty approach-able and you can chat with them easily. Rachel can be really sweet (even though she isn't always sweet on stage).
All of the above comments I would not disagree with: you all seem to feel out the band pretty well.
Regardless, I always love seeing them live. They are fun and they play fun music (even though some shows are better than others, I've never seen them suck live). When they start playing, the room seems to get much happier because the music is good for the mood.
All I can say is, even though they are a cover band, check them out and I don't think you'll be disappointed.