I've ridden a lot of bikes, from 13hp 125's to 180hp R1's.
The FZ6R sits in a really nice niche for a street bike, with plenty of oomph up to 180km/h. It can go faster but it feels like it has to work for it, and after 25 yrs of riding, I am no longer interested in what the top speed of a bike is ~ we have a local 'short' track here where the bikes top out at around 210km/h, so to be able to get to 180k without a lot of drama is good enough for me.
Although there are Supersport bikes that will go faster, you also have to rev them to 13,000+rpm, which just feels like so much work to get the thing to GO. You can't go anywhere these days without getting a photo radar or speed-on-green ticket anyway.