I wouldn't recommend it for most people as a first bike, but if you feel comfortable now on the gsr600, and respect the size and power of the Rocket, you'll do just fine. It is very possible to ride it slowly and smoothly, at least at first
. It doesn't "need" to be run hard, but if you pull back on it's ears it will reveal the beast within.
As
@Mongler07 said, good general riding skills and training will go a long way toward your ability to get proficient on this bike. It handles great on twisties and once it's rolling it doesn't feel so big and heavy at all. It's a very unique and fantastic machine.