Honda CBF600rr

Agreed, 400's are not for everyone. if you can accept it for what is it then great - enjoy
if having the latest, newest and need to score highly in the pub top trumps bullshit stakes then an old 400 simply won't cut the mustard.

Real life and real world now, a sorted (and by sorted i mean a proper example of the breed, not some ebay shitbox £1000 bitza project) 400 is a wondrous thing, less so for a tired on baggy cheap dog eared example.
however they also weigh nearly just as much as a modern 600 too, even if they do carry their weight a bit better.
Some parts can be hard to come by, they will do around 130 flat out and thats it, and they are simply old and need a bit of mechanical sympathy and care and effort.

My advice too would be to buy a modern 600 and enjoy it. a CBR600FX FY FS or F1 are all very light examples of the CBR range, are user friendly and bastard fast when you wind them up too.
they are everything and for 95% of the time are better than the later RR models for day to day road use, and for most normal folk are probably quicker from A - B too with the increased feedback being a bit softer and lighter.
I appreciate some with read the above and shout "bollocks" but after owning both its the older FY i keep and not the later RR.
RR owners will love the RR because it is exactly that, happy to sacrifice the low down grunt and midrange power for that extra kick up top when thrashed - and of course the stunning looks of the RR

They will also be much cheaper than a good 400 too

Anyway i don't want people buying 400's - i aint got them all yet.