PickupStix

I'm looking for advice on installing a new, preferably preprogrammed ECM on my 2009 GMC Sierra. Flagship 1 has a bunch of good reviews, but there are also a noticeable amount of bad reviews. Are these reviews people who don't understand that when you have an E0100, that you have to do your due diligence to troubleshoot before you call the issue a "bad ECM"? Should I order from them or buy a unprogrammed ECM and go to a dealership? Please advise.