Avail in .243 and others. It's bigger than a standard AR-15, because the .243 Win is based on the .308 case, so it's basically a version of the AR-10, not the AR-15.
Found a deal on a used .243 upper at a gun shop a while back but decided not to put the cart before the horse.
Have to watch the bullet weights if you get one. Armalite claims theirs may have problems cycling properly with the lighter bullets; <75 grains, maybe?
Some of the guys here are using the DPMS rifles in "tactical" competitions and doing well with them. I can't remember if they're using .308's or .260's...
Another fellow I know ordered a .308 DPMS last fall, and is literally having a blast with it. Very good accuracy, and of course he can rip off three or four shots in a big hurry when he wants.