The 'free'
DDP (available for all bookings made before Nov 6 this year and good for holidays up to and including Sept 29, 2007) is indeed a valuable extra being offered at the moment for all Disney resort guests, but it is dependent upon buying either the Ultimate or Premium ticket (if you book with an operator in the UK) or a length-of-stay Magic Your Way pass if you book direct with Disney in the US.
How can Disney afford to do this?
Well, simply put, they are counting on selling a lot more Ultimate, Premium and MYW tickets than they would otherwise have done without the 'free' incentive, so some people will end up buying more ticket than they actually need (and Disney will get more overall revenue as a result). That will also mean more people in the parks, more people spending money in the parks on gifts, souvenirs, etc, and, again, increased revenue for Disney.
It also means people will be less inclined to go elsewhere (i.e. Universal, SeaWorld, etc) as they become a 'captive' audience; if they have already paid for a length-of-stay Disney ticket, they will want to get full use out of it, hence they are more likely to stay on site. So, Disney's overall revenue goes up, and the others' go down.
DDP is also a slightly complicated daily points system that people need to add up and co-ordinate themselves, and there are sure to be instances when people don't get full value from it because they don't understand it. Disney's restaurants are also getting more and more crowded for the duration of this offer (for both counter service and sit-down dining; we noticed it quite markedly already last month), which means people need to book dining in advance to be sure of getting their table service meals in. If people don't do this, they simply won't get in to some restaurants, and they may opt to eat elsewhere, thus also losing value from the dining plan.
Overall, it is a pretty shrewd marketing plan, as there are no actual price increases (apart from the one-day ticket prices last month and the jump from $9 to $10 for parking this month, neither of which should affect on-site guests) to claw back the 'free' element of the dining. But Disney ARE counting on more people spending more money (and fewer going to Universal, etc) so, if you are equally shrewd about using the plan and just doing what you want, we think you CAN benefit from this in the short term.
However, and purely as an aside to all this, we found Epcot, Animal Kingdom and the Magic Kingdom all much more frenetic than usual in the latter half of August, notably in and around the restaurants. Consequently, both Universal and SeaWorld felt much calmer and more enjoyable by comparison, and the quality of attractions is just as good. If Disney DO ever succeed in forcing the other players out of the market (and Universal's big drop in attendance last year is certainly a warning sign), it would be a very sad day for Orlando and, ultimately, very bad news for those of us who enjoy going there.