A Thundercat is an awesome bike. I sold mine to buy my Fz1 but purely because I wanted something newer and with a bigger engine.
They are very large for a 600 which I found to be a good thing, plenty of wind protection and not too much of a severe seating position, the clip ons are above the top yoke so your only lent forward slightly (compared to modern sport bikes anyway)
The power is all there if you want to play, 100bhp when new and i can personally asure you they do over 140mph (if thats you thing)
Under seat storage is decent, pillion carrying is alright providing you have a sorted shock.
Only downside to them is their age, lot have been used and abused, "modded" with shit parts or just generally run into the ground. Also servicing ext is a bit of a faff as the old fashioned sports fairing is put on in about 900 pieces so you need a good 20 minutes of stripping down just to get to the oil filter
Running costs are next to nothing even my insurance was dirt cheap as the insurance company didn't class it as a supersport (because of the r6 being the same year) so that was a bonus.
All in all I don't think you'd go wrong with a decent one. I personally plan on buying another when I have the space and using it for trackdays and general hooning
