It's a shame that they styled it like a Cavalier/Grand Am. Great drivetrain but the styling was about 8 years old upon introduction. Imagine what the GTO could have been if they actually did more than "badge engineering".
Ya, that does seem to be the most common complaint, that the exterior is fairly bland. You have to remember though that the original GTO came from a car similar to the Grand Am. They took the fairly economical Le Mans, put the biggest engine they could into it and renamed it the GTO, so they remained pretty faithful to the namesake by not making it a flashy sports car. And for a car that is styled "like a Cavalier/Grand Am", I still get a thumbs up or a comment from a random driver or pedestrian on a weekly basis (or both in the case of last week, a guy on the freeway giving me a thumbs up and then yelling he wants one too).
But your right about it not selling well, there was even a manufacturers incentive at one point that was $6000 off msrp (I got mine about $5000 under msrp in late 2004 if your wondering). If you can find a new one still on the lot (and it wouldn't surprise me if there were still some around), I have no doubt you could easily buy it for $10000 under msrp. A large part of the problem was a lack of advertising, I think I only ever saw one commercial for it and that was on the Speed channel. I'm sure the fact that the exterior doesn't catch ones eye hurt it a lot as well, unless you've already been told about the car, you'd have no idea what it was just by looking at it.
If you can't tell, I like my car and have no problem going on and on about it

I actually wrote at least twice as much as I posted, but I decided to edit it down so I don't come across quite as bad as Howard C talking about scifi (and if you read this Howard, you have to admit you have a tendancy to be a bit verbose, so hopefully you won't take offense to this)