I agree with most everything everyone said here. I bought one of the first Rockets made and my situation is somewhat unique in that I seem to have a driveshaft spline problem which some, but not every owner has had. Just make sure that the driveshaft spline is lubed with Honda moly 60 or another similar lube at every tire change.
If you plan on driving long distances, buy a touring seat with gel. I have driven my Rocket more than 700 miles in one day and the standard seat won't cut it for that kind of driving. Same if you have a passenger. The standard pilion seat is just a little old pad and the wife only lasted 50 miles on it. The touring seat takes care of that. I would also highly recommend a backrest for the passenger. Of course they now make a touring model so if you bought one of those, the seat would not be an issue.
Others here have mentioned the power. Be careful with throttle movements the first few miles until you get used to it. A little "blip" of the throttle goes a long way on this machine. Also when you downshift the first few miles, go easy. The first mile I drove mine I had to downshift for heavy traffic and the rear wheel almost locked up on me when I let the clutch out a little too fast.
Overall, considering its size, it is a very friendly machine. It is relatively nimble in city traffic and stable at high speeds. I have had mine up to 130mph and didn't notice any shakes or vibes until around 120. I have driven it at 110mph for about 30 miles and was very comfortable. I don't recommend doing that; this was on an isolated 4 lane highway in Canada but it just demonstrates the abilities and characteristics of the machine.
The early advertisements for this bike said that it was friendly but needs to be respected. I have found that to be very true.