I can see where if you watch ONE channel, a la carte would be for you.
But if you (or you live in a household who) want say, ESPN, CNN, COM, AMC, FOOD, and FX (bear in mind, not everyone will be subscribing to these channels, so I imagine they would cost more than they do now in order for the networks revenue to not be whacked) I would not be surprised at all if just that random package cost almost 75% of what a full cable package costs now...at which point, I'd rather pay the additional 25% to keep all the channels I currently get.
I don't like my cable bill now thru Directv, but they typically work with you on price to save a couple hundred dollars a year.