I've now purchased an early FZ6 with 14,500 miles. I sold my FZS600 a year ago. I've read all the stuff and I was a bit apprehensive about buying it, but so far I'm pleasantly surprised. The FZ6 rides well and feels similar in many ways to the FZS600.
Now going through the process of cleaning, servicing and checking everything. It's an 'honest' bike which has had basic servicing but needs some TLC. One thing I hadn't realised and seems very silly is having the battery up top at the front. The main reason I love the 600s is because they are lighter and change direction much quicker on the road. I don't like 'top heavy', although to be honest I hadn't felt that. Found the battery today as I wanted to add my optimiser wires. I also found some corrosion under the tank - surprised Yamaha didn't fully spray it with a good coat under there. It's only light, spotty bits of rust so for now I've just cleaned it up and added a coat of clear Waxoyl.
Next job will be to try and remove Exhaust header nuts, remove then prepare to get some paint back on the front of the engine.....
Cheers, Clive