My first street bike was a Honda 350 twin and later I owned a 400 four. The 350 was just a great little bike. Super reliable, the only quirk was an timing chain through the center of the jug that wasn't removable without dismounting the jug. We solved that by taking off the valve cover and breaking a link by grinding off the peen on the pins and replacing it with the master link from a 500 four's timing chain. After that, no problems at all! Although like griz said, points and carbs, so get friendly with a mechanic or learn to do it yourself.
That 400 four was absolutely a pocket rocked! I recall splitting lanes, racing a Sportster at 100 mph. The bike was nowhere near the redline but with other traffic around that was faster than I was willing to go, and faster than I should have been going. Still, that would be a great bike to own, given that same (points and carbs) restriction.
The 750 is plenty of bike for cruising. And all of them are air cooled, no radiators to worry about. Harleys are nice, but these are the bikes that opened up motorcycling to the masses.