They ARE quick, and can challenge a CB750 (if the latter's rider isn't on his toes). At speed in top gear the 550 is a smooth hiway ride, too. We sold a lot of them in my shop, and not one complaint ever. One guy bought his in the Spring of 1972 ($965 out the door) and rode it from Illinois to Alaska and back on the (then dirt) Al-Can Hiway with his friend who had a Norton Commando. When he got back to our shop that Fall the bike was held together with duct tape, forks and swingarm were bent, still [sort of] rideable, ran OK with 40k miles on it. He said the hiway did it in during the trip, he was on his 5th set of chains & sprockets. He junked it and bought a 750 the following Spring.
The Commando didn't make it home, BTW...