My dad owns a 2004 Bullet classic, and it is BY FAR my favorite bike I have ever ridden! That 500 single is the most charming powerplant I've ever delt with. You can almost hear every revolution, you can hear the air sucked into the engine and pumped out! You can hear all the valves (they are very loud) working. The riding position is perfect (IMO) and the handling is immaculate. These little darlings weigh under 400lbs. The braking is terrible by today's standards, but the bike only has like 20HP.
20HP doesn't sound like a lot, and it isn't. But the low end is where it counts. Cruising back roads at around 40mph is what this bike is made for, and I have yet to have a motorcycle experience that equals it. Don't expect to use highways, this old girl works HARD to go 65mph, and that's with slightly higher gearing than stock. I've never had it past 70! But, because of the low compression and low RPMs you run, you'll get 65-75 mpg!!
Now, having praised this, my favorite motorcycle, I must admit to its faults. Yes, the electric start is s$%t. We have used the kick start since it broke. Trust me, after learning to kick a 500 vintage style single, you can kick start any other engine!
The build quality of components is aweful. Springs, controls, cables, all of the little bits are low quality. But you can replace them easily. The engine, though, seems quite bulletproof. It's never been apart so I don't know about the quality of crank bearings and such, but we've got something like 15k on this bike and it runs like a top. It is, however, buring oil and leaking a little. My dad thinks it's time for rings. But, on this vintage style engine, a job like that is no big deal. You have one cylinder to deal with.
Parts are pretty easily available and there are many aftermarket upgrades available.
Don't buy an RE expecting a reliable, everyday rider unless you are willing to maintain it constantly. It needs regular valve adjustments, regular chain tightening (which is kind of a pain on this bike) and all those things you guys are used to on your hondas, just to a larget extent. In fact, unless its run regularly, expect a simple start up to take a couple of minutes. Peter Egan once wrote that you have to think of starting an old (or retro in this case) bike as a task in itself. You can't just hop on and go!
As for the new aluminum engines, I don't know. The iron block has been made for centuries and seems reliable. I don't recommend fuel injection or electronic ignition, that stuff doesn't belong on a 50s style bike (IMO of course). If I were to buy my own Royal Enfield, which believe me I would LOVE to, I would go with a used model just because that iron block has been around forever and I also prefer the styling of the older models.
In sum, I highly recommend a Royal Enfield, but only if you are willing to deal with old tempermental technology and low quality componentry. I like the "task" of getting the RE running and a low-stress cruise through the country is an incredible experience on this bike. And remember, a highway bike this is not!
Good luck and I highly recommend trying one out!
Jeremy B