Should you be getting ready to cry some more?
Alright, welcome to the first DLC review I've ever done. Because of the way that DLC works this is going to operate a little differently then a normal review. Rather than giving a letter grade, this is going to be a recommendation that comes down to a simple yes or no, with some explanation given as to decision. This also assumes that you have bought and played the base game, in this case The Binding of Isaac, enough that you're considering purchasing Wrath of the Lamb but still find yourself unsure.
Title: The Binding of Isaac: Wrath of the Lamb
Release Date: May 28th, 2011
Base Game: The Binding of Isaac
Recommendation: Long story short if you played and enjoyed the original BoI then you should buy this DLC, especially if you've completed most of the original content. With a price tag of roughly three dollars WotL adds a lot of new content that can make the game fresh again to veterans of the original experience. The current downsides are some minor glitches being worked out and some strange difficulty curve issues, but those shouldn't discourage purchase of this DLC.
Okay, that was the short version, so here's the long one: Wrath of the Lamb is a DLC that's worth purchasing, but if you're only getting the original Binding of Isaac now, then I'd actually actively discourage you from getting the DLC right off the bat. The reasoning is two-fold here; first and foremost is the fact that at the moment this is DLC that you cannot undo: once you install WotL you cannot turn its content or options off. The second reason is that the alternate levels are more difficult for even seasoned veterans of the game. The Cellar for example is a lot tougher than the basement, and you have no choice over whether you get one or the other. Any new players should play through the game and at least build up a good cache of unlocked items, combinations they are comfortable with, and a working knowledge of the game before diving head first into the deep end of the pool with this expansion.
That's not to say that WotL isn't worth it. In fact the more of the original game you've completed, the more millage you're going to get out of this expansion. There's a lot of new items, as well as a new character to unlock, new bosses, a new alternate final level, boss, and ending, and additional things like the ten challenges you can take to make the game harder or just different.
The odd thing is that with the new content the game can occasionally seem a little unbalanced. The Cellar alternate opening levels I mentioned above have a spider theme that extends to the enemies, and the spider versions of a lot of foes are faster, tougher, and a lot more annoying then their regular counterparts. This makes runs, especially ones with glass cannons like Judas and the new character Samson -- can be frustrating and short. I wouldn't go so far as to give a condemnation of cheapness, but it doesn't seem entirely on the level. It's one of the reasons why I'm not recommending this DLC to new players, because even veterans are going to have to relearn things, and having to deal with everything at once might be a good way to ensure that someone just starting out will walk away and not come back.
That concern aside, Wrath of the Lamb is a welcomed addition to Isaac's universe, if only for us, and not for him.