This car is very, very fun to drive (for those who like sporty cars and sticks). It gets excellent gas mileage while still being pretty quick. The interior is very nice, with some cool Si-only touches. I got a crazy good deal on this car used, but I'm not sure if I'd like to pay full price for it new. It's not quite as quick as some of its competitors (only 160hp). But, it outhandles most of them, and, importantly, it has just about bullet- proof reliability. Most other "Pocket Rockets" are pieces of junk with powerful motors (like the Neon SRT-4) but the Civic Si will still be perfect 100,000 miles from now.
The seats are easily the best of any car in this class; they're made by Recaro, I hear. This car handles like a go-cart. The dash mounted shifter is in exactly the right place, and shifts smoothly (except into reverse; it'll get there eventually, but you have to fiddle with it, even from park.)
MP3 compatible radio (I use an AUX input converter.) Better wheels/tires. Engine swap from from K20A3 to K20A2 (in Euro Civic SiR or Acura RSX Type S) if you NEED more power.