Driveability:
I drive mine to work every day that the sun is out. With the cam I have it idles pretty rough but almost never stalls. Never floor it on a curve and expect the tires to spin at anything under 45 mph going in a straight line. It's hard to handle in the rain, it's nearly impossible in the snow.
Economy:
I think it is just as economical as a stock SC until you stick your right foot into it. As a rule..you tend to burn more gas and rubber as your hp increases.
Reliability:
Get a second car. Once you go over 350 hp, you can plan on things breaking more often, much more often. Instead of thinking in terms of "can I go another 100,000 miles before rebuilding" it will be more like "can I make it another month without working on this damn car"
Fun:
You forgot to ask if it's fun...Yes it is very fun !
David