Hi Paul,
My first bike was a 2000 R6 (which I lost a month ago to thieves ) and I absolutely loved it. But the first few weeks on it were a nightmare. Trying to get used to the twitchiness, lack of grunt below 8000rpm, NASA launch like kick after 10000rpm and the fact that doing a u-turn without jamming your throttle hand and having to put your foot down is harder than eating soup with a fork.
BUT, and this is the crucial part, everything I mentioned (apart from the u-turns) I got used to and actually became the reasons I loved the bike so much. How I miss it......
The advice from the other guys is all sound though so basically you have to have weigh up the pros and cons and do what's right for you. One thing I can guarantee is that if you do get the R6 then you won't be disappointed but your adrenal gland is going to be seriously overworked.