BellKicker,
if you are a strong candidate, you don't necessarily need to be "cleared" (ECFMG cert, Step 3) to get a prematch offer.
I've got an offer and signed a contract with step 1 and 2 scores only, still waiting for my CSA results. The program promised to sponsor my H1, eventhough I got my Step 3 results just this week.
Having said that, I would have preferred if the prematch had not been an option. I had a couple of interviews in programs with much better reputation, and it took my a lot of soul-searching before I decided to sign (the main reason was that I wanted to stay in the city for personal reasons and all the other programs in that area are top-notch where my chanced were probably slim). It is very likely that I would have ended up in the same program if there was no prematch, but I wish I could give my dream program at least a shot.
The major advantage of the pre-match, as secretwave101 posted, is that you have more time to get through the paperwork. You might need to get some documentation from your medical school, and this takes forever in my country. In spite of this, many IMGs go through the Match, and manage to have their paperwork ready in time to start their residency in July.
So all it takes is maybe to move the Match results release a couple of weeks earlier?