I am a fan (and you should be too), because...
first, the music is amazing, of course. If you don't enjoy the music, anything else is irrelevant. Although I don't know how anyone could not love it. There's something for any taste on their début album; not since Duran Duran's Rio, or Bon Jovi's Slippery When Wet have I owned an album I could listen to start to finish every time!
But beyond the music, this is a band full of great, down-to-earth guys. Most of us here know they could have gone straight to opening at arenas, or even headlining at smaller ones (judging by how fast the smaller venues sold out and how many who wanted them didn't get tickets). But they instead choose to play small intimate venues and be closer to the fans knowing that they likely wouldn't have that opportunity later. They give us the chance to know who they are. After playing hard on stage, they often came out to mingle with those who waited and are happy to stop and take pictures and chat with those waiting outside before shows. They check in with us periodically even taking the time to do video blogs to let us know what's going on with them, always thanking us for supporting them. Their accessibility and willingness to take us along on their ride has earned them an extremely loyal fan base in a relatively short period of time. We love them; not only because they are talented musicians, which, of course, they are; not only because they're cute, which, of course, they are ;o); but also because they acknowledge and appreciate our part in their success. They not only allow us to feel a part of their lives, but make sure we know we know that we are. They take the time to make us feel important to them, and that makes them that much more important to us.
