I admit that I have only owned one AR. (so far)
However, I have HELD (in store) a Bushmaster Carbon 15. To me, it felt extremely "plastic like", but that is only an opinion.
However, that being said, according to the MSRP on Bushy's website is $865.86 (strange amount, IMHO).
So, I would have to say that if you can get one for $500 plus tax....and it's what you want....then it's a heck of a deal.