I'm reluctant to speak for Berliner myself. Let's see if this works.

The QGA is outside my wheelhouse.
Berliner dismisses 5...Bb4+. My copy of MCO-13 considers Bb4+ the only move too.
I found Berliner's System exciting as I first browsed through it. Berliner is, or at least was, a substantial intellect at chess and computers. He's definitely brighter than I am.
Nonetheless, as a programmer I've dealt with really smart guys from Ivy League schools and I notice that, as wonderful as they are, it is easy for many of them to get carried away on their own BS and it's hard for lesser mortals to rein them in.
By the time I checked some of the lines and finished browsing "The System," I got a definite whiff of eau de crank.
But I enjoyed the ride and I like it when people roll the dice on intellectual longshots.
@ipcress,
*Before I post comment I understand you are neither condoning or condemning Berliner's approach.*
I'm also a software developer so understand exactly what you mean. The pragmatism is sometimes lacking.
Berliner's system is interesting but there are so many deviations before it gets to some of those critical exchanges that I can't really think of this as a refutation.
While 3.e4 is certainly a sharp move it isn't even the mainline by a long shot. And the response 3..e5 and 3..Nf6 are played about equally. That's a great example of what I meant by the comment that if a line fell under a shadow the QGA offers a number of viable alternate lines.
Let's just say we sat down for a number of hours hand waving, analyzing, punching in computer moves and we all came to agree that Berliner's line was correct. Then we'd simply switch to Nf6. Or worst case we might try a delayed form waiting until after we played Nf6 before play cd.
Somehow though, with 3.Nf3 being played 4 times as often as 3.e5 I have to think that Berliner's observations are probably incomplete if not incorrect.
Thanks for cluing me in to the source of this line being Berliner and Korchnoi! All I knew was that around 2003 I saw the position after 1. d4d52. c4dxc43. e4e54. Nf3exd45. Bxc4Nc66. O-O and immediately liked it, because it looks like a Max Lange type gambit--like the game started 1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4 and suddenly the c2 and d7 pawns vanish and white plays 0-0.
By viewing it this way, you can look at all the typical open game moves for black and get a sense of what to play next. If 6..Nf6 then 7 e5 or if 6..Bc5 then 7 Ng5. The most popular move is actually 6..Be6.
Fiveofswords: Here's Hans Berliner's take on the QGA according to his System.