OK, nearly a month in with the FZ6 S2 (after 6 years odd with FZS600). Key differences that stood out to me:-
Tank range! 130-140 miles until fuel gauge starts flashing. Vs 200-230 miles on my old 2003 FZS600. And flash bar on fuel gauge doesn't really catch your eye... But I do like how it switches to the FTrip and counts up your 'reserve' miles. I know 130 miles odd is about normal for many bikes these days, was really spoilt with range of the old Foxeye.
Torque. The FZ6 feels more torquey, more low down grunt, and arm yanking as you set off. On paper, there's not much in it, but it's definitely noticeable on road.
I'm gonna say it doesn't feel quite a flickable as the FZS600, but I'm not sure if that's just me not so accustomed to it or really the case due to design, different front tyre size, or even tyre brand (have switched from Metz M7RR's on FZS600 to Mich PR5's on FZ6). But definitely handy to have more tyre choice with the slightly fatter 120/70 front.
Getting more vibe in pegs of FZ6, and I see there's rubber grommets on mounting too. Clutch feels heavier and not convinced by the free-play adjuster which appears to only lock on whole 360 degree rotations.
Seat position, legs/knees seem to fit in a lot better around tank/frame. Though do find seat-to-pegs distance a bit tight for my lanky legs, which can make rear brake usage a bit achy after a while.
Under seat exhaust, is nice and warm on ass this time of year, daughter loved it going pillion last weekend. But I don't like losing loads of storage space, and I do wonder how I'm gonna like it in height of summer...
Not liking the FZ6's single headlight design, dipped on left, main beam on right. Have ordered some wire to do the headlight mod. And will probably add extra spot lights later too. Commuting in London, need everything you can to stand out in traffic! Do like how dipped lights don't turn on until engine starts - good plan, could be handy if battery is ever low.
Givi rank seems to sit further forward, making things much tighter space wise for pillions. Especially with top box with back rest bolted on.
Mirrors on FZ6 don't hold position so well at FZS600, always need re-aligning after slightest nudge of removing rain cover.
Indicators hanging down from fairing on FZ6 - looks a bit naff. But probably a good choice, as in a drop, indicators often broke the fairing on the FZS600. Similarly, interesting to see separate fairing side panels where it would invariable get scuffed in a minor drop.
Servicing:
Spark plugs are a fecking nightmare to get to. Haynes books says remote radiator, tank, air box and battery, for every 6k spark plug gap inspection - WTF?! Got in there with spark plug tool from under seat kit and spanner, after loosening off radiator mounting to prise it slightly forward without disconnecting. Really need a ratchet spanner set though...
Replacing air filter on FZ6 is much easier than the FZS600.
Miss the oil eye sight window on FZS600. Dip stick gauge is more faff, removing, wiping, dipping etc.
Do like coolant filler on rad on FZ6 S2, rather than hidden under tank. But coolant overflow tank on front of engine is a shit location, cover is already corroded to fuck on a bike that's done only 12k and been garaged all it's life... At least it's cheap to replace.
Like how shock is less exposed to elements on FZ6 too, should help longevity.
Split fairing infils seem a good idea to aid access when lifting tank, again seems to be a practical design choice to aid servicing.