I'm a fan (and you should be too) because...
You can tell that there is so much passion in Brandon's voice when he sings, and the warm feeling it gives you makes you feel good. I know it makes my day. I keep a CD constantly in my car, so that when I drive I have uplifting feelings each day.
It's so obvious he (and the band) are all very creative and artistic, just by the lyrics and ever changing and growing sound.
I think that when you look at a painting from a particular artist, you see what his mind sees and feel what he feels. You can go "there" with him.
When I listen to Incubus, it takes me to a soothing place, kinda like Cloud 9.