The Civic Si is a well-rounded economy sedan with some great performance features...a 4-door S2000 it clearly is not, but you can easily see the design influences throughout the car. Ergonomics are fantastic for a car in this class...the steering is very good, shifter is better than 90% of all sporty cars out there, and handling is better than I expected. Seats take some getting used to...I almost yanked mine and installed Recaros during the first week of ownership...but got used to them after a 1600 mile drive. Overall, I am very pleased with the car.
The K20 motor is almost as much fun to push as the F22C1 from my S2000...again, almost. The rest of the drivetrain works well...partial thanks goes to the hydraulic clutch. Being able to plug in an iPod for my 1600 mile trip was also great...sound quality was superb.
Nitpicking: there's nothing wrong with this car that 20 more horsepower wouldn't cure. The only real change I'd make is to the seat fabric...it really picks up the lint. Maybe change the seats, too.