Gas piston guns, are you going to get a good one for under $1000?
I have some very wise friends and when we first started to see the piston driven AR15s show up on the market “again” about 7yrs ago, it was mostly debates about the AR18, the LWRC piston driven firearms and the POF guns. I think POF did a good job of staying in the market up until about 2yrs ago. Now everyone and their dog is making one but I would still caution anyone from jumping in the fire and expecting theirs to be up to what LWRC is making. The only argument you can make against LWRC guns is probable the H&K 416 variants.
Even with some of the earlier LWRC M6 rifles, there have been some changes, modifications and uprgrades. I was fortunate enough to have been able to go to the LWRC factory and upgrade on of my LWRC AR15 upper receivers and get the new bolt carrier group without any altering of the firearm I have. My LWRC M6A2 is a much older version compared to what is out now the barrel life is about 4x’s more. There are still large variations in piston driven uppers and I got to shoot a Ruger 556 last year and was very impressed with the quality of the firearm, there may be more choices in 2012 and many of them look nice, but will there be modifications or changes to them and getting parts for yours might become harder and harder in 2-3yrs.