Yea I'd say there was possibly something wrong. I recall the 07's having bad mapping initially? and as a result Subaru offered a flash update, to which owners noticed a considerable power gains to what they should be. I think you honestly should test drive another STI before getting the wrong impression about them.
And agreed about not all STI's are ragged on. I'd say a good percentage owners in their late 20's or older take care of their STI's. You can't really judge because its a bargain performance car that every 18 year old has ran it into the ground and is selling it to you. Just use common sense and get the car checked out or inspected for yourself before you make a final decision.
I think if you plan to have the car a long time and do a few mods, you will greatly appreciate how well the Subie responds and holds up to them over the MS3.
GL with your purchase.