Is the
DDP (or QSDP or DxDP) right for me? This is a very subjective question, and as such requires a very subjective answer, though backed up with a bit of fact and analysis. Everyone is different, with different objectives and priorities, and as such, it is doubtful that any given two groups of people, even if going to the same places at the same times, will agree on the relative benefits (or lack thereof) of any particular dining plan.
That said, there are some basic rules of thumb to consider. Table service meals (except room service and pizza delivery) pretty much require making reservations; it is very difficult to secure table service seating "on the fly". As such, some people may not wish to be tied to a schedule -- these people will likely not enjoy the DDP or DxDP, though the QSDP may be an option for them. In a similar vein, people who do not want to feel "committed" to using a set number of credits within a certain time window may find that any of the plans are too burdensome for them.
As a personal opinion, if you qualify for the purchase of a Tables In Wonderland (TIW) card, it's probably a better option. The savings will probably be as good (within some margin of error) as any of the dining plans and there is more flexibility and less commitment involved, although you will need to use the TIW card enough to justify its cost; on a single short trip, this may be hard to accomplish -- for multiple and/or longer trips, the cost can be more readily absorbed by savings. Note that there are some dining plan locations that don't take TIW (and vice-versa).
Otherwise, the general advice I try to give is: if one of the plans matches (at least closely) the way you want to eat while on vacation, then it's probably a good idea. If you're changing your dining habits to match the plan, then it very well might not be a good "deal", regardless of any apparent (or real) savings. If you tend to want to order off the "low end" of the menu and would rarely want desserts, you might not see any savings on the dining plans at all!
The "intangibles" of having a dining plan is knowing that everything (within reason, and generally excepting tips) is already covered -- it makes for a more "all inclusive" experience and allows you to be a bit more ambitious in ordering items that you might not take a risk on if you're paying for each item out of pocket. The flip side is that it could also lead to some stress in trying to ensure that you "get everything you're entitled to" and attempting to "maximize" the plan, rather than simply dining the way you want to at that moment.
So, back to the first principle: everyone is different, and will accordingly see a subjective value (or lack thereof) in the dining plans differently.
Now, of course that doesn't answer your question directly, because not knowing more about you and your preferences, I can't really advise you on something so subjective. However, the points raised above should get you to thinking about which -- if any -- of the dining plans might fit your own style and preferences.