I loved this episode...exciting..well acted...and very clever.
Hume as a philosopher believed in Free Will...but for Free Will to have any meaning Hume believed there had to be Determinism.
I think this episode incoporated that idea quite well. I also like that instead of Time Travel...the classic Sci-Fi idea of alternate universe could have applied. Especially at Desmond's first prediction of the come from behind victory in the Football match.
My first thought was he had switched over to another quantum universe were one of the different outcomes was the victor/loser of the match.
For those that are clammering for simple reveals at the end of every episode...no offense...but I think you have sucked the life out of the show for yourselves and are missing the point. Stage and TV and Cinema are performance arts...and performance arts are as much about the journey as they are about the destination.
You dont watch a performance of Who's Afraid of Virgina Wolf to just find out if the couples stay together...you watch for the process. Lost has great personal witting and great actors that pull it off.
Lost is a show that can pull off making the process interesting, compelling, universal. I think everyone can empathize with Desmond's dilemma, making a choice, again, that will cause you extreme pain, keep you from the person you truly love, and be given the appearance of a coward, even though your choice was in some ways brave.
Now compare that depth to the interpersonal episodes of BSG, it is like watching Ibsen and then watching a Kindegarden class...."Lee is paying too much attention to Kira, I want my cake and eat it too, I'm right and you are wrong"....blah...blah...blah.
Now BSG is a show that should SOLELY stick to moving the plot.