Not a great deal
You figure that sight is roughly $400, which would then put you paying $1100 for the M&P15OR, which is above MSRP (granted not by much). It's not a bad deal, it's just not a "you must jump on that" deal.
It's a great price compared to February's prices, but February's prices are history. If there's not much available in your area and you don't mind paying MSRP for the EOtech and rifle, it wouldn't be a bad pick up. If things keep going the way they are, you'll probably be able to get it cheaper by looking around a bit. On the other hand if another wack job shoots up a school tomorrow then the $1500 cost of it today might be the best price you ever see for that set up. But is that really a way to live life?