What is the current preference and opinion on lower brands? Bushmaster, DPMS, Olympic, does it matter?
Ralph stay away from all those that you mentioned. If you want highest quality go with a Colt, Noveske, LMT, LWRC. Other great companies are Stag, Anvil Arms, Spikes Tactical to name a few.
Most (but not all) of the common forged receiver brands come for a handful of OEMs. Some brands handle finishing themselves, but many are 100% identical.
For example, my Fulton lower is indistinguishable from a DPMS; both are LAR receivers. Spike's and Noveske are supposed to use LARs as well.
Stag and Rock River use (or have used) CMT receivers, and Colt was rumored to have done so as well. Stags are certainly fine receivers (although I can't get past the "queer deer" logo myself).
It has been suggested that Bushmaster has used LMT receivers. I don't have an LMT to compare it to, but the best fit & finish lower I've personally come across has been with a recent Bushmaster.
Don't discount Mega receivers... Coleman Tyler has a good deal on re-branded Megas ($111 as of today). IMHO, they're a bit nicer than the LARs, but not as good as the LMTs.
Superior Arms seems to manufacture their own receivers, and there's discussion that they also provide lowers for Anvil. They have a good rep.
Take the above with a grain of salt; the brands in question usually don't disclose who provides their receivers, and sometimes source from multiple manufacturers. The ARFCom guys keep a close eye on the minute differences between the brands. More info here:
http://ar15.com/forums/topic.html?b=3&f=12&t=318113
Finally: the general consensus seems to be that all of the above supply damn good lowers. Don't get too hung up on the brand... the differences between forged receivers are mostly cosmetic. What you install for your trigger group, upper receiver, and barrel will make all the difference.
