Just replaced my radiator. I was expecting it to be a complete b***h of a job, like most things on the WRX engine, but not too bad. Only took a couple of hours.
10+ years for the original radiator isn't bad. The core was fine, almost perfect. Split top plastic tank, coolant sprayed everywhere.
I pulled the tanks off, so I could recycle to aluminium core, and I was pleased to see the core was very clean. No residue at all. Guess that means the previous owners looked after the car. :-)