Excellent choice! I know you'll find DD to be a fine rifle that should be largely problem free. Over the years you'll be glad you paid a little more for quality.
I bought their M16 bolt carrier group for my AR build when I decided to have a spare of this critical assembly. (Actually put the DD in my rifle and the original back as the spare.) Very impressed with the quality for only $129 and it meets all the important specs for a BCG.
You don't hear many bad things about Daniel Defense.
BTW, it is the DPMS AP4-C that appears in the M4 Comparison Chart, not their lower cost models. And it only scores 3 out of 21 (ignoring warranty and rear sight). It's worth a look at that link someone provided earlier to see how fine your DD is.
Last edited by Quentin2; September 13, 2010 at 12:54 PM.