*All WAR numbers in this article are from BBRef
On June 4, 2009, the Pirates dealt Nate McLouth to the Atlanta Braves for Gorkys Hernandez, Charlie Morton, and Jeff Locke. That Pirates team finished 62-99 (missing the magical 100 loss mark by the grace of a rainout of an ultimately inconsequential game). Those Braves finished 86-76; good for 3rd in the NL East, 7 games back of Philly and 6 games behind the wild card-winning Rockies. This ESPN article calls the trade "a move to beef up Atlanta's offense in hopes of contending in the NL East."
Like Morgan, Nate the Great was in the prime of his career (he was 27 at the time of the trade and didn't turn 28 until after the season. McLouth wasn't terrible in 2009 for Atlanta: he did post a 1.5 oWAR for them in 84 games. His defense, however, sunk his value for his Atlanta career. dWAR's of -0.7, -1.2, and 0.0 dropped his overall WAR numbers to 0.8, -1.4, and 0.8 for a grand total of 0.2 over the 2 1/2 seasons he spent there.
Charlie Morton threw 97 innings for the Pirates in 2009 and posted a 0.7 WAR. Then, in an effort to out-suck McLouth, he put up a -2.5 WAR in 2010, but then bounced back with a 2.3 WAR in 2011 for a total of 0.5 WAR overall. That alone out-values McLouth's tenure in Atlanta (though pitcher WAR vs. batter WAR is shaky at best). Jeff Locke posted a -0.2 WAR over 16.2 innings in 2011, his only time with the MLB club. Gorkys Hernandez has not made his debut for the Pirates, yet.
Recapping: just comparing their MLB WAR, Atlanta got 0.2 WAR out of this deal while Pittsburgh saw 0.3 WAR. Incredibly undwhelming numbers. Atlanta paid McLouth $12+ million (not sure how 2009 was split) for those numbers. Ironically, Pittsburgh countered that by signing Nate as a free agent this offseason for 1 year and $1.75 million (which I think if a gross overpayment, but it's not $12 million, so I suppose it's a minimal risk). He's still technically in his "prime," but Atlanta got his 27-29 seasons when he should have been at maximum value.
Morton is just now in the middle of that range. He just turned 28 and had a much improved season in 2011, showing some flashes of serious potential. Jeff Locke just turned 24. He struggled in his cup of coffee last year, but he's a lefty who's averaged over 8 K/9 and about 3 1/2 K/BB in 6 MiLB seasons. The Baseball Prospectus list from a week ago (BD link) puts Locke at #12 in the Pirates system. Gorkys Hernandez, considered the centerpiece of this deal (#62 prospect before 2009 according to BA), hasn't reached the majors, yet, but appears at #19 on that Baseball Prospectus list, has some speed, by all accounts plays good defense, and is still only 24-years-old.
The numbers aren't as high as they were in the Hanrahan-Morgan deal, but the result is the same. Atlanta only got McLouth, who is no longer with the club and cannot put up any more numbers for them. Pittsburgh got some young players with talent who have showcased some of that talent and remain as assets to potentially acquire more talent (especially Hernandez, who seems very unlikely to ever play regularly in Pittsburgh at this point). Pittsburgh has already banked more WAR than Atlanta did, and at a massively cheaper price. I know that vet-acquired-for-playoff-run is often the recipe for a hindsight-lopsided trade, but the Braves didn't exactly get Doyle Alexander's crazy 3.9 WAR from 1987.
If I can pile on: the earlier linked ESPN article from 2009 says "With the trade, Pittsburgh cleared a spot for one of its best prospects, 2005 first-round pick Andrew McCuthen." All he's done is drop an 11.5 WAR since taking over for Nate McLouth. Pittsburgh thoroughly fleeced Atlanta, getting back 1/300 of its pride from Black Wednesday.