Thats a great price for a great rifle. I have the M&P 15T and love it! I put an EoTech on it, a hogue grip, forward grip, and a blackhawk single point sling. I have had no issues with it at all. I have close to 2000 rounds thru it with no issues. I have fired brass ammo and the newer wolf steel cased ammo with no issues.
These rifles are Mil spec and are a quality rifle. They also have a great warranty.
If I could find one for that price I would buy another.
Go for it.....you wont be disappointed. Plus you could get the 15-22 as well.