Head Room is awesome - I feel like a midget driving this car. However, I usually drive with the seat one or 2 clicks forward from all the way back on most cars. On the WRX, I am all the way back, but it's just right. I also run around with the seat height adjusted all the way up for visibility. If you lower it, the legroom improves significantly.
I'm 6'1" and I have the seat height set to the lowest and I have enough room to straight up. I used to have a civic before too and I had to always pull back the ceiling (the moonroof) or else my hair would be touching the ceiling... speaking of moonroofs I kind of miss it!
I'm 6'3" tall with a 34" inseam in my pants. I typically drive with the seat raised up fairly high for visibility reasons (plus I find it more comfortable). However, I like (only just recently) to keep the seat closer to the steering wheel than I am used to. It helps me brace myself on the dead pedal easier and find that I am better able to control the shifter and the steering wheel when driving the car hard. I have had no problems with lack of room in the WRX.
In my other car (1970 Datsun Roadster), I am constantly hitting my head on the top, whether it be the soft top or the hard top. I usually solve that by taking it off (it is a convertible after all).