One of the benefits of having been around this forum for three and a half years is that I have read a LOT of these types of posts. One individual's anecdotal experience is irrelevant, but I've seen enough different people relay their own anecdotes to make some conclusions.
There are a LOT of these complaints (and have been for years) about MoreBeer.
There are much, much fewer complaints (although, to be fair, some) about Austin Homebrew. Seems like a very high percentage of our membership shops at AHS, so it doesn't seem to be more than a marginal amount that has had complaints.
I don't think I've seen more than one or two complaints ever about Northern Brewer, or about MidWest.
So far, zero complaints that I've seen about Brewmaster's Warehouse (or Rebel Brewing, for that matter). Those guys are both pretty new, though.
I've been lucky as hell so far, I suppose. The majority of orders I've placed have been through NB, with nary a single issue or complaint. I've ordered from Forrest a couple of times, no problems, and now from Brewmasters' Warehouse without issue. I've deliberately avoided the first company listed, because there are a metric ****-ton of these threads complaining about their inventory weaknesses out there. Until it's fixed, why futz around? I've never seen their prices as really being cheaper.