My insurance went DOWN. I know it makes no sense, but who am I to argue with the company
Few things to keep in mind:
2006 was first model year. For 07, fuel map was updated to smooth out throttle roll on and 06 comes with a stiffer rear spring. Now.. you're used to FZ6 so even 06 FZ1 will feel like the off/on throttle is smoother, so I wouldn't be too concerned

. Stiffer spring is not a bad thing, especially if you do any 2-up riding.
Price is good, but have you considered going for a used one? I picked up 07 with 8k miles on it in basically new shape (and several expensive mods) for $5k.
Reasons to get FZ1:
1. Better fork
2. Less vibration
3. Much more progressive clutch
4. Better headlights (proper reflectors on both sides for low/high beam)
5. Power! Loads more torque AND power .. it's a much *lazier* bike.. there's no need to rev it out to make it go. Having said that, the power really is not brutal.
6. Much better aftermarket parts selection.
Reasons to keep FZ6:
1. It's a damn fine bike that can do everything well and in my opinion is easier to throw around in turns.
2. FZ6 is lighter (though not by much, but it certainly feels lighter).
3. FZ6 gets much better fuel eco (~45 vs ~35).
Not a complete list, but at least some of my ideas. All in all, I'm very happy with FZ1, but I was very happy with FZ6 too. Both great bikes.