In the world of MMO's (and other MM type things), the idea of Microtransactions seems to be akin to the devil's penis being inserted in a newly formed orifice that every player has grown.
What the hell?
There is a good, and a bad side to microtransactions, as with everything else.
Gives non-serious/hardcore people a reasonable shot
Some unique vanity items
Exclusionary (to poor people)
Can give an unfair advantage
Here's the thing though, I both like & dislike transactions. And I'll give a few examples of the good and the bad.
A good microtransaction: There's an item in WoW called "Ashes of Al'ar". It's a mount, the Phoenix one, that drops off a raid boss that no one is doing anymore. A good MT would be to sell it for 7$, and have at it. This example would be great. Or another is, one of the top staff's in the game currently is the "Spire of Scarlet Pain". It's a good item. Instead of going through the complete hassle of farming for it, why not just sell it for 10$? There's two riders on this idea however. 1. The Spire is a purple (epic) item. Why not make the bought version blue, or red, or something? Keep all the stats on it, just a different text color, to differentiate it from the dropped version. And 2. The way the WoW store is set up now is insane. 10$ for a pet, and 25$ for a mount is over the line. I'd say a price drop is in order, maybe 5$ for the pet, and 10$ for the mount. Possibly 15$ for the stuffed animal (with mount), because that's an actual physical item.
A bad microtransaction: The way TF2 does some stuff. Don't get me wrong, the way TF2 does items is usually fine. The more you play, the higher the odds are that an item drops. It's not super hard to comprehend, and can be fun. The issues I have are two fold, one the prices (fairly insane, like WoW's), but the other issue is the Mann-Co Supply Crate drop. So, let's say you do get a Crate drop, how do you open it? Well, you have to BUY a key to open it. There's no way to craft a key, although it can be traded from player to player. So, in order to use the item (or find out what's inside), you have to buy an item to activate it? Does this strike anyone as a bit fishy?
In the end, I think Microtransactions can be a good thing. It's just a matter of the company doing them, not being greedy about it, and offering players who put in the time special value. Now come on Blizzard, sell me the Headless Horseman's mount.