If it's not an Impreza I'm guessing you're talking Liberty (Legacy in non-Aus markets).
Depends what you're looking at really. If it's relatively unmodified and has a full service history (ideally dealer for at least the first three years or so) then you should have an absolutely bulletproof car that will be ultra reliable and will go on and on for ever.
Be wary of Japanese imports with little history, especially modified GTs/Turbos.
If you can stretch to a 2004/5 model year Liberty then do - it's a huge improvement on the previous model.
If you're looking at standard models rather than the performance GTs and B4s, the 2.0 is a more reliable unit long term than the 2.5 quad cam.
Much of the same applies if you're looking at a Forester.
I'm on my 7th Subaru, one for each star in the badge.
