Best open class sportbike period. I own two of 'em, but selling both for a new 2006 R1 Limited ($18,000!) and a black R1 standard I've got ordered. Minor changes for '06 include a longer wheelbase, 3 more HP, re-valved fork and shock, stiffer frame... nothing drastic. Kawasaki's ZX10R is too hard edged and unrefined, same goes for the Suzuki GSXR1000, a rocket fast bike which I think is kind of crude and too cramped and uncomfortable for anything else but track use.
I have a '05 Repsol CBR1000RR and a black '04 CBR100RR also, and these are easily the most flexible and easy to ride 1000cc bikes, but the Yamaha R1 is just awesome...rev happy, with quick, snappy response, a superb chassis and perfect suspension and brakes. The 20 valve Genesis III engine is the benchmark of refinement and durability. All this, and it's built like a Swiss watch, just damn beautiful to look at and touch. Can't beat it! The Hayabusa is a completely different animal...it's not a "sportbike" by today's standards, more like a "GT" bike. Heavy, long wheelbase, stretched out ergonomics. Better for long cruises, but any 600cc supersport will eat it alive on a tight track, that is, as long as there 'aint any long straightaways where the 'Busa can hit hyperdrive!