I'll echo wyosmith. While i'm not completely building my own, I'm building a lower and then buying a completed upper. It'll feel a lot more like my /own/ weapon than just buying one off a shelf.
Edit: That being said I've heard a lot of mixed reviews on SigSauer ARs and mostly negative on Bushmaster.
I told the new me,
"Meet me at the bus station and hold a sign that reads: 'Today is the first day of the rest of your life.'"
But the old me met me with a sign that read: "Welcome back."
Who you are is not a function of where you are. -Off Minor