Isnt the consensus that it is/was Desmond's boat? Isnt the finale Desmond's flashback?
I think it is Desmond's round-the-world sailboat as well. Moreover, here's a few random thoughts I had after watching "3 Minutes":1. Desmond is on the sailboat Sun sees at the funeral. After he ran off, he prepped it and was going to sail away from the island but he has now succumbed to the "sickness" - that's why it appears the boat is just drifting in. Remember, he had been injecting himself with the vaccine and I don't believe he took any when he ran out (am I remembering this correctly?). Perhaps once you are on the vaccine and then go off of it, you are far more vulnerable than if you've never been on it.

? Maybe. BTW, I think this will be a Desmond flashback as he's on his deathbed with the sickness (50/50 as to whether he recovers to be part of Season 3. I'm leaning slightly toward no recovery as I think the flashback will provide all the Desmond info we'll need to move forward.) But if that's the case...
2. What happens to Aaron when that limited supply of vaccine Charlie provided runs out? Or is it any good now to begin with? Remember, everything Charlie does, nothing seems to turn out right. It would be so like this show to have him perform an act of kindness that ends up causing major problems (particularly since Claire seems to be warming to him again).
3. Back to the boat. Recall Sayid saying that they needed to think of an advantage against the others as Michael leads them into the trap. Might be a little farfetched to think that they can sneak up on them from the sea in a sailboat, but maybe if they do it at night?