My Blackbird's fecking ace! It's just DP that says their crap, but he's a dyed-in-the-wool Kwak man so he'd rather have a ZZR.
Good things about the 'Bird:
It's (very) comfortable
It's not bad in a corner
The linked brakes are actually pretty good (despite the fact that reviewers seemed to enjoy moaning about them)
The brakes are *big* - stops pretty hard
The engine. You could go on for days about the engine - it's smooth, torquey, powerful, and revs so high you can kick god in the nuts. Needs an oil change every 6000 miles and a service every 12000, so it's not even bad for that.
Below 5000rpm it's a pussycat. Over 7000rpm it's a psychotic device designed to induce panic.
Loads of luggage options if you're touring.
Bad things about the 'Bird:
It's a bit thirsty on the fuel (well, it is an 1100 after all)
It's quite heavy. Fully-fuelled it's a quarter-tonne. Don't drop it. When it's moving, though, you don't notice.
It's a big machine. Filtering will be fairly different to your Thundercat. I found it hard work at first, moving from my Divvie, but it's okay when you get used to it - you can squeeze through most traffic. Just expect to clip those expensive mirrors once or twice.
Rear shock is an excellent unit, built down to a price. Overhauled, it becomes a brilliant part.
Electrical regulator/rectifier is made of crap. Worth upgrading.
Some people complain that the mirrors are too small / show only shoulders. I've not had a problem, though.
90mph is easy. 100 is easy. 110 is easy. 120 is easy. 130 is easy. 140 is easy. You get the idea - watch the license. It'll only go as fast as you ask it, but it's very tempting to ask for a big number.
They have a bit of a reputation for eating chains. I'm refitting my Scottoiler.
Overall, if I didn't have mine, I reckon I'd be in the market to buy one. In my mind the good points far outweigh the bad points.