I apparently started this long ago, but finishing a PhD and moving to the Middle East left me unblogging for quite some time. I'll leave this as is and try to finish what I started.
With the new D&D Next playtest packet, I've been avoiding the forums and what I presume is the vast amounts of nerdrage over the new packet. My first thought was disappointment because of the loss of options: Clerics and Rogues really lost a lot of options and there was no sexy new bard to make up for it (though the druid and barbarian may have decent updates). Anyway, I did some reading about 2nd edition, and came to a few conclusions.
1) Second edition is maligned because it is transitional and unfairly gets criticisms that should (also) go with other editions.
2) Second edition is misremembered: things that people complain about in third edition didn't apply in second edition (and earlier).
3) Second edition is really three distinct versions: core, complete, and options.
I'm going to focus on the first and third aspect here, but mostly the third.
The grognards hate second edition because they feel their particular version (original, b/x, becmi, AD&D 1st) achieved perfection in the 70s and nothing that happened once TSR's mid-80s problems hit is valid. Let's face it: grognards don't even like things like Oriental Adventures (see the comments here and here) or Unearthed Arcana by-and-large, and the modules from the late 70s and early 80s are considered the best. Grognards forget that adventures changed midway through AD&D 1st edition. So any grognard criticism is largely going to be that 2nd edition isn't their edition of the game. But it is a legitimate continuation of what was happening in that version of the game. It is pretty obvious that you can convert second edition materials easily to earlier editions of the game than third or fourth edition stuff.
Now, the core 2nd edition books (the big 3 plus Tome of Magic and Legends and Lore) actually make a pretty coherent little system, and in that respect they're just a clean-up of the first edition AD&D rules, with a bit of sanitization to help avoid the Satanism stigma. So gone were assassins and half-orcs and devils and demons. But in were the specialty priests, specialist wizards, playable bards, and such. Interestingly, also gone was the rule that gp=xp. I think this falls in the realm of sanitization too, because xp for treasure induces the murderhobo style of play, rather than heroic parties. Though xp for gp was an optional rule. But by and large, 2nd edition started out as a cleaned up and sanitized version of the game. You can criticize it for lacking Gary's tone, but I think even Gary would have bowed to sanitization and ditched monks, assassins, renamed devils/demons, etc. He wouldn't have been happy, be he probably would have done it (and done it somewhat tongue-in-cheek). When I go back and look at the early edition stuff, I wish it had as much variety as is presented here. Specialist wizards and a couple priest variants would really help tempt me to play a real old-school game.
Next, comes second edition complete, with all the complete handbooks. This is the start of the splat-bloat, but this is nothing that other games and companies weren't doing either. From a business stand point, TSR needed people to buy more products, so calling them T$R is just a naïve lamentation about capitalism. This started to have more "broken" shit, but a lot of it was still solid. I think some of the problem is when new complete books came out, you could only integrate that material with new characters. Unlike third or 4th edition where you could take some feats/powers/spells, the new stuff in second edition generally required a new/redesigned character.
Finally the option books came out with character-points, spell points, proficiency points, and all other kinds of points. I think Combat & Tactics and Spells & Magic were fairly solid. But people forget that these are collections of optional rules. You didn't need subabilities or to use those point-based character creation methods. You could just use the new schools of magic, new priest classes, or critical hit charts. So while those books may have some crazy shit in them, you weren't instructed to use all of that.
When people hear 2nd edition, they start thinking of the end of the run, 1995+ rather than the beginning, which is the opposite of 1st edition. When people think of first edition, they're actively excluding Unearthed Arcana, Oriental Adventures, Dragonlance Adventures, and the like. Third and 4th edition have the same splat-bloat as second did, so there's really no grounds for criticism there: the bladesinger from Complete book of Elves can't be much worse than the junk that came out in 3.5 or twinstrike for the 4e ranger.
In Essenece, I think second edition gets the flack for a number of things that were happening in RPGs at the time. First, a trend towards story and heroism that started in the mid to late 80s. We certainly see it with Vampire but it seems the trend is apparent in dragon magazine. Second, the addition of options and rules to the game, which started with first edition AD&D (Many OSR folk don't like races distinct from classes, monks and other sub classes, or Psionics) and continued with Unearthed Arcana. These two really do go together: a more complex story demands more character options, in a sense. You see this trend in the Options books where they tried to revitalize the game with insights from other games (point-based design).