I'd like to get a 5.56 piston type black rifle but it doesn't necessarily have to be based on the AR15 design. I have an M&P 15 moe that's a great rifle but I still want a piston. Does anyone know how well the M&P 15 PS/PSX compares to others that are on the market? Is the PS/PSX pretty much trouble free now that it's been out for a while? Sure I lean towards wanting the PSX but is that just bias on my part?