Fingers had a huge impact and was a big part of Jimmy's sound, if not half of his sound. It hasn't been the same since he quit and the songs he had such a pivotal part in since he quit when they're played live just sound... flat. Not that Fingers' leaving is necessarily a bad thing for Fingers (although he may have regretted it privately), it's just there have been a lot of songs where I wish Fingers was playing (for example, it would've been sweeeeet if he was on Tonight I Just Need My Guitar).
Fortunately he did play on Everybody's On The Phone on TAKE THE WEATHER WITH YOU, which is fantastic.
But considering Fingers had to swallow such pathetic crap like Cultural Infidel and Math Suks I don't blame him for leaving Jimmy when Jimmy kept coming up with such incredibly astoundingly suckass songs like Party At The End Of The World, Wings, Big Top, We're Still Here, Useless And Important Information and Turn Up The Heat And Chill The Rosé... just to mention a few.