I play in a Classic Rock cover band, but the reality of it is: we play EVERYTHING! Jazz, Blues, Country, and smaltzy wedding songs! (Please cry for me!)
When I bought my first Mesa, I was doing harder rock and playing louder--but even with this band, the Mesas are perfect gigging amps. I try to match up the amp to the size of the stage and venue, but sometimes it's just a whim as to which one I take.
I think the biggest fallacy of thought when it comes to Mesa amps is that they don't get good clean tones. I think the clean tones are really good. I have a bass player and a keyboardist in the band--so the low end would get really crowded if I used an amp with a huge bottom end, like a Fender. My clean tones are great!
And nothing sings like a Boogie!
I use multiple guitars, with a G&L Legacy as my main guitar; and then a Les Paul. I usually have another G&L (one with hotter pickups) as a backup; and then there's often a 12-string, a Taylor acoustic-electric, and a 5-string banjo. The Mesas get great tones, no matter which guitar I'm using, with minimal fuss.
Bill