i have had 2 impreza's, and he same number of rs's.
a few people on here always go on about the melting/knocking of bottom ends, but mapped properly they will be as reliable as any cossie.
the problem is some people who import the japanese cars think that they will run perfectly on uk fuel, which is wrong, mapped properly for uk fuel the car will be fine,
my last impreza was a 1998 sti 4 import and mapped for uk fuel and achieved approx 330bhp on optimax!
overal the cars themselves are nimble, handle well when aligned properly (4 wheel to either prodrive settings or grd if down south) and if maintained will last a long time!
tuning wise, they are getting cheaper to modify, looking in the right places will see you up to 300-330 for about £800. thats if ur not fussed about buying second hand parts!

the only down side is that the car is beginning to get into the hands of young drivers and the insurance is becoming silly in some areas