I just bought Wrath of the Lamb, and am totally hooked on The Binding of Isaac again! If you haven't shelled out the $3 dollars for it yet and are even remotely interested, I highly recommend it. It makes everything way more crazy, even more random, adds tons of new items, environments, and enemies, as well as a host of other features. It also automatically provides the new songs if you have previously bought the soundtrack. For three bucks, or eight if you don't already own the game, I must say it is a very solid purchase.  

An excellent expansion to an amazingly addictive game. I've watched a guy on youtube play this for even more hours than I have played myself, but it is always entertaining.

I beat the game for the first time with the expansion. It was intense and awesome.

I still have not beaten the original game. Even when I get an awesome character, something really bad happens and I die. :(

Stick with it, I played it like 60+ times before I made it to moms heart.

Biggest tip for beating the game: don't get sloppy, even when you get good items. You have to constantly try the utmost to dodge pretty much everything and take as little damage as humanly possible. To that end, don't even worry about aiming carefully in hectic rooms, just so long as you're holding down the shoot key; instead, focus most of your attention on dodging things.