Bought my STi from Subaru of Plano last year, and I wish I had gone somewhere else. It was a truly awful, horrible, nightmare of an experience. Nothing but bull**** and incompetence. Stay away from SoP at all costs!!!
I've been to Sewell Subaru a couple of times for maintenance and they seem great, but I've never purchased from them so can't say for sure. It's a hell of a lot nicer of a dealership than SoP, I can tell you that much.