I went from a 20 year old Honda Hawk (650 twin) to a 600RR. The biggest hurdle I had was getting used to the high pitched whine of the higher revs. I knew it wouldn't make any power low in the revs, but it just sounded so... wrong. Just keep telling yourself it's *supposed* to sound like it's going to blow up. (assuming you're not actually over redline.)
I went from a BMW K1200s.. 4 times... then Instructor Gun/Nick said best to get an SV and learn wtf your doing. I actually followed his advise for 2 mfn years. Learned tons on cornering/ corner speed etc. as my mind was free from worrying about insane speeds. -- then added a bmw 1000rr. omg.. and it worked great. All my turning skills transferred. Everyone said be careful of the 1000. But it's like a dream.. I can flick it just as good or better then the SV into the turns, and its' so much more comfy.. I now ride both.. but love tht dan'g 1,000. -- I would never recommend starting on a 600 or liter bike. You'll never learn.. Pay your dues with low HP, and learn wtf your doing first.