I've had mine for not quite 2 months, a DVP serial prefix, seems to be the latest. No issues with mine at all with Federal bulk 550, had a couple FTF with some Winchester super X, but I've had trouble with my supply of Super X in every 22 gun I have, about 10 of them.
I've followed your issues with your 15-22 and can understand your frustration, IMO I think you would love the newest model out, you seemed really happy with your current model when it worked right. I can't imagine you getting two lemons in a row.
I bought a Sig 522 over the weekend for my son (the discounted OD green model), will shot it tonight. Break down between the two is about as easy, aesthetics is about the only difference I see in pre shot condition. One thing I will say is I like that the 15-22 has the full length rails, although the OD green 522 does come with 3 4" rails that mount to the side and bottom of the front gaurd. The 522 doesn't come with sights either.