hi. i have a 08 z1000 and love the machine. i didnt have a katuna but had a yzf600r before hand. your girls zzr600 the yzf600r and katuna fall pretty much in the same class cept the katuna is a bit more comfortable than the 2 600's.
the difference in seating position is what youll notice most as well as the increase in power and torqe. seating is an upright standard position which is pretty comfortable on your wrists legs and back. the one thing that will kill you is the seat itself. that thing is cardboard thin and will start to kill your ass in about an hour,maybe less. definitly upgrade to a corbin or have the stocker reupholstered.
power and torqe will be a dramatic increase that will do this to your face

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as long as you respect the bike youll be fine. as far as wind protection, you will have none. i myself dont feel like it is so crazy that it makes it difficult to ride or feel that it fatigues me. its just wind. cruisers ride through wind all the time and dont whine about it like most s/s bikers do. yeah the yzf had awesome wind protection but who cares. i know i dont.
honestly i think youll love the bike. just remember that the zed will eat up more gas and also take 90 grade and up. so fuel consumption and cost will go up a bit. another thing is that you will not have any trunk space. invest in a tank bag and youll be fine.
there are going to be small things that your gonna miss your katuna for but plenty of other things your gonna be glad you upgraded for as well. if you do buy a zed you will find that the it is an awesome real world street bike.
good luck ride safe and always wear your gear!!!!!
oh and before i forget check out this site it has plenty of info about the z1000's
Kawasaki Z1000, Z750 & Z-750S - RiderForums.com Community