Great looking bike. Perfect step up from the 300.
I miss my 300
If I saw one on CL for under $2500 with ABS, I'd snap it up.
I'm not sure I go with "perfect" step up from the 300. The 650 is a different class of bike, it's more in the sport touring class with those high handle bars and very upright riding position.
Where the 300 makes a pretty good track bike, the 650 doesn't. It's difficult to get in to the proper body position if you want to take this bike out on track making it difficult to ride. (Though it can be done and you can have a lot of fun.) The upright body position is great and the bike is comfortable enough that you can climb on it at 7AM and ride until 9pm that night. I rode it 350 miles on Saturday then took it out and rode 950 on Sunday. I would have gone back out Monday if that pesky work thing hadn't gotten in the way. It was just that comfortable.
Coming off the 300, if you're more interested in a more upright bike for the street this is a pretty good bare bones bike. There's not a ton of mods you can do to this bike. My 650 has a single piece exhaust. So if you wanted to change it it's a full exhaust or nothing. The front suspension has absolutely no adjustments which means buying a new set of forks or slapping the ZX6R front end on it. At least on the rear you can adjust the preload on the spring.
I'd put the 650 solidly in the good first bike class. It's good on the streets. It's fun in the twisties. You can build your skills at track days. But, eventually you'll outgrow this bike's potential at the track. Once you ride something from the supersport class on track you'll wonder how you actually ever rode this thing.
So, depending on what you want to do coming off a 300 you may want to look at the 650. If you just want to cruise around on the street on a bike that looks sporty but is very comfortable, then maybe this is a good step.
If you're interested in developing your skills and maybe having some fun at the track, then I'd stay away from this bike and look to the ZX6R or another 600 class bike. If you don't think you're ready for a 600 class bike then stay on the 300, you'll learn more on it than you would on a 650. (What you'll learn coming off a 300 for the 650 is that you should have stuck with the 300.)