I have heard few complaints about Spikes. Although i remember seeing pictures from one guy who chopped a reciever in half with a band saw once because he said it was so bad out of spec LOL
I own one of the older ones, but they have bought completed stripped lowers from several sources since then.
(they don't actually make their lowers or uppers). So, based on different sources, the finished products will vary. Last I heard they were using Aero Precision, which cost about $30 less than the Spikes' roll mark and Aero also make the Surplus Ammo and Arms and Palmetto State Armory lowers, which are often on sale for around $50.
If you want to drink the SPIKED kool-aid, that's OK, they're not really bad, but you're buying into a name. I own various brands and don't really think they're any better or worse than most any other reciever out there.
Not trying to ruffle anyone's feathers, but you asked an honest question and I gave you an honest answer.