I also have not ridden the 1500, but I will tell you my experience. Prior to owning my 900 Custom, I had 380 pound sportbike. I wanted something more comfortable and built for longer rides. I love the 900 custom. I will admit that driving it home off the lot, it was very intimidating. It wasn't the power, but the weight that I wasnt used to. Going from 380 lbs to 615 lbs was weird at first. I must say though that it was extremely easy to get used to. Going into turns, I was shocked how the bike basically pulled it self through, without much effort from me. Even at low speeds, I find the bike extremely easy to manuever. I was nervous making a turn at 5 mph out of the dealership, but once I got used to the bike, it was a blast, even at low speeds. I would say it took me about 2 days of riding before I was 100% comfortable riding at all speeds. Also, riding 2up and low speeds is a little bit of a challenge on any bike, the extra weight (regardless of how skinny she is) will totally alter the center of gravity of the bike, and it will be most noticeable at low speeds, especially on turns.
Now to the Highway aspect. Does the 900 hit high RPM's when riding on the highway? yes it does. To be totally honest, I ride on highways every day at actual cruising speeds between 70-80mph. I have cruised at these speeds, steadily for 2 hours without any issue. The high RPM's has never bothered me one bit, and even at those speeds, trust me, there is plenty left in the throttle. You could always replace the front and rear pulleys, which as previously stated, will not only give you a more accurate speedo, but will lower the RPM's...
My advice would be to either test ride the bike and see if you notice a difference at low speeds, and even if you bike the bike, if the RPM thing bothers you, you can fix the issue for fairly cheap
I hope this helps ya a little...good luck
2009 Vulcan 900 Custom
Vance and Hines Slash Cut Staggereds
ShowChrome chrome accessories