I regularly criticize the people behind the Mac App Store. I call them all sorts of names because simple things don't work and if you ask for help, the support people know almost nothing and handle almost nothing. For a company whose service is supposedly a high point in the industry, the company should be fixing this weak point.
e.g., I had a situation where the Twitter and Typist applications could not be downloaded. Other applications could be downloaded within the same time frame, but (only) those two downloads would not happen for anything. System software updates were fine. I was told that my connection was the problem.
So, yesterday, I was at the Kenwood Towne Center mall, at the Apple Store to buy AppleCare for my almost 1 year old refurbished MacBook Pro. While I was there, I talked about buying Final Cut Pro, and the associate went to some lengths to get me an Ethernet cable and a direct connection to their intranet, so that I could buy and download it.
I had not updated my debit card's information. The Mac App Store looped and looped and looped, as I furiously attempted to update the information again and again. I finally disconnected, put things away, and left the store. I never saw that associate again, so I couldn't thank him once more. Once I was home hours later, I was able to fix the information.
Seeing MacRumors earlier, there appears to be a widespread issue: http://www.macrumors.com/2013/12/05/some-users-unable-to-log-in-to-app-store-due-to-fatal-error/
Apple is such a mix of great design, haphazard testing, and a don't-care attitude. That they're ahead of the rest of the industry suggests that we should all feel sad that things are that pathetic. I noticed that a lot of my co-workers in various software development assignments weren't disciplined, and the code they wrote was sloppy in the extreme. You would think that Apple, Google, and Microsoft would have the best design, coding, and testing procedures in the business, but none of them do. A smaller company like Adobe should be better, but they're even worse. At least, when John Warnock was there, they seemed to care about more than money.
In any case, Apple missed a sale, although I doubt they're crying about that.