Some of the suby guys will chime in, but as Subaru has established a significant reputation for reliability, as long as the car has been properly maintained there shouldn't be any major issues.

Look through its carfax, if there's multiple stops at the dealership for scheduled services that's a good thing. If not... it's too hard to tell without getting it up in the air what could be wrong with it... and even then things have a tendency of surprising you with that kind of mileage...