Larry Jr. sounds like a winner. One suggestion I read was to do 4 deaths against a Horseman, getting a cube of meat each time, and then letting Meat Boy do the rest. That seemed a bit daunting to me. For one, I hate the Horseman, so beating them 4 times with 1 heart sounds no fun. For two, my issues were never really with firepower with this, it's hitting that one crummy room that either decimates what little hearts I have, or has me trying over and over and over again (I seem to always encounter crap like tight walkways and those worms that rush you, or rooms with like, 6 of those fat dudes that shoot the creepy little biter creatures from under their trenchcoat/stomach).
This idea sounds much better, so thanks. I'm at about 57 hours myself, so I'm happy with 16 Mom kills and 2 Satan kills. At this point, Satan seems like a synch, after my first soul crushing go at him. We'll see how Isaac goes. Reading about it makes it sound extremely daunting.