I used to have a major thing for the Chili Peppers, I basically taught myself guitar and bass by learning all their songs. They miss Frusciante I think though, I like some of the newer stuff but he was great to have for the live shows.
I've not seen them without him, but I can bet they would be missing something as he would be impossible to replace. They rocked Wembley last time I saw them, but that was nearly 10 years ago now.