This is spot on, really. I remember watching Orton his first few years in the league -- my brother-in-law is a Bears fan and season ticket holder, so we're both up on each other's teams -- and he was bad. Really bad. He certainly seemed to find something those couple of years in Denver, but while he was in Chicago he was nearly unwatchable.
Like you said, though, I'm not taking anything away from his current play. He's doing well, and I hope he continues it, of course. But I don't see him as a long-term solution.