I own a 2003 S2K. The car is an absolute blast to drive and own.
Has the typical Honda reliability. Mileage is 23 to 24 all around. You can easily get 30 mpg at highway speeds if you keep the top up. Of course that is not much fun, so I always drive with the top down and get a bit less economy.
If this will not be your primary ride, then you have an even better argument for getting one of these great cars. A 97 Honda Prelude is my every day ride (a great car in itself too) and the S2000 sits in the garage ready to go when I get the urge for some extreme driving excitement.
Don't let the lack of low end torque bother you. The S2000 provides a different experience than a muscle car whose high torque rumbly V-8 puts out gobs of power at low RPM's and starts to level off at around 5500 RPM's. If you are used to that, it will take some time to appreciate having the power at the higher end of the RPM scale. This baby redlines at 9300 RPM (2003 and older models, 2004 and above redline at 8000 RPM with power kicking in a little lower in the RPM band) and is amazing when reved up to that level.
For 2003's and older, power kicks in/enters VTEC at aproximately 5500 RPM's (when most engines are starting to level off) and does not really drop off as you approach readline. On 2004's and newer, the power kicks in at a lower RPM level. The incredible 6 speed manual gearbox makes it very easy to manage all this high end power and keep the engine running in the sweet spot. While I love the low end torque and rumble of a small block high performance V-8, I much prefer the screaming sound these VTEC engines make at high RPM's. I would best describe it as exotic. It takes more skills (easily learned) to get the most out of these cars, but well worth it in my opinion.
The handling of this car is precise/razor sharp. The front to rear weight ratio is very balanced. It almost feels like you are driving a go-cart.
Now for the flashaholic aspect of driving an S2000. Another great feature of this car is the HID headlights. There are many that believe these are some of the best HID headlights you will find on a production car. The lighting is perfectly focused, projects a rounded pattern and covers a wide width going considerably out beyond the sides of the road. When on night drives down twisty back roads, I often spot deer that I know I would never have seen without the benefits of well implemented HID lighting. The best way to describe the experience of driving with these lights is that it feels like you are "pushing a disc" of light in front of you.
For more info than you could ever want on this car check out the great S2K International forums:
http://www.s2ki.com/forums/index.php?act=idx
The temp is in the low 80's and absolutely gorgeous, so in a couple of hours when it cools down a bit, I will going out for a quick spin with the top town to carve up a winding road or two!
Let us know what you decide to do!