I'm now 47, and my SM is my first bike. Excellent choice.
I have learned to really appreciate smaller cc bikes since I started riding and reading so much about them. I'll toss out the Triumph 675 as a good example....major horsepower and torque numbers even compared to our bigger machines.
If you are looking for a cruiser-styled bike, you can't beat the "cool factor" and reliability of these two (Speedmaster or America), and for a beginner, I found mine to be very forgiving when learning to ride it. The long wheel base gives us an added measure of safety when compared to a shorter wheel-based sportbike, in the event of a rear brake "panic stop" tire skid...if you let up on the rear brake pedal you just might be able to save your hide without going down. I have on a few different occassions, and know I have the bike to thank for it.
I'll bust 36k today, and the bike was only 3 years old in June. Took a 750 mile, two-up trip to the Hill Country last weekend with my wife aboard - our first trip - and I can say that these bikes are big enough to do anything you might ever want to do, or go as far as you might ever want to go. I am sure others here will chime in. A heavier bike might not blow as easily in a cross-wind, but these are certainly manageable. Plenty of power and room to get comfortable in the saddle and pillion to.
I consider the SM a sportbike, or sport cruiser, with it's more aggressive riding position, and the America with it's pull-back bars more of a "cruiser". I ride mine hard, rarely ever loafing it anywhere.
My motto: NO PUTT-PUTTS!
