I became a fan in April 2007. Pretty late and I totally regret it.
I realized the greatness after I've, by chance, found Spiral's blog and decided to give them a shot as there were some SBD bootlegs. I think it was Elevation in Sacramento that led me to think "WTF, I didn't know they were so great live!" and downloaded some more bootlegs. The more I listened the more impressed I was by their live energy, so the more curious I became about them (only knew some greatest hits): I watched youtube clips and read bios. Really everything I found out was what I was looking for in a band/musician: music, meaning, fun and humour, passion, social conscience, attitude.... I've had this love for artists before, but not in the extent I developed with U2. Feels good.