I started out on a Suzuki GN250, which, back in the 55mph speed limit days, was plenty. Now, with 80MPH being the normal traffic flow on interstates, I feel a 250 is a bit lacking, unless you plan to stay in town. The 500 still has plenty of power in reserve at 80, but is still a oy to putt around at 20 in the neighborhood.
I went straight from that 250 to a 2-valve 650/4, then to a 5-valve 700/4, and my other bike is a 4-Valve 1000/4, but is actually not as fast as the 700. I've been riding for over 20 years now, and got the 500 for my fiance to learn on, but instantly fell in love on the first ride. I've been riding it far more than the Concours, and figure I'll either keep the 500, or replace it with a 650R, which is the sucessor to the 500, but only when the used 650R prices come down more. The only reason I consider the 650R is because it weighs about the same as the 500, but has the same style engine with more power and better ergos. For the money, the 500 is in a class of its own.
The 500 has been a real blast, and is a perfect bike for beginner and experienced rider alike. I've been turning the 500 much more agressively than I ever turned any of the 4-cylinder bikes, and the confidence it gives me has translated into helping me take the corners faster on the bigger bikes.
I squealed the front tire, while braking, today for the first time in many years. I had reached that point on the 250, but was never able to get myself to do it on the bigger and heavier 4s. Again, the confidence the little 500 has given me has translated into helping me stop more quickly on the bigger bikes.
So the 500 helps teach old and young dogs new tricks, and since it has the power and handling to keep up with anyone riding at sane speeds on the street, is something you don't have to get tired of in a season. Of course, if you put it in your head that you WILL be tired of it, then you will be...