I just recently bought a Bushmaster M4A3 Patrolman's Carbine (earlier this month). It seems well made. 4150 Steel chromed barrel, BCG is chromed plated inside and gas key is staked well.
Upper and lower fit well together. I've only put 180 rounds thru it but there were no malfunctions. Shot both .223 and 5.56 with no problem. It was accurate right out of the box.
Nothing wrong with my Bushmaster, I just wouldn't pay MSRP for one tho. Mine had an MSRP of about $1200, but I got it for half that online and I have seen them for as little
as $549 after mail in rebate.
I'm not saying they are the best brand out there, but they are not the trash that many people (who have never even owned one) say they are.
If you are looking for a good entry level AR, Bushmaster will fill the bill. Just don't pay $1200 for one.