I low carb during most of the year, well I try to anyway. But I'd find it very hard to do the DDP and low carb. The biggest problem to me would be the appetizers and the desserts. It's hard to find good low carb appetizers and almost impossible to find low carb desserts.
We just decided to go from 10 days on DDP to only 3 days on DDP mainly because I'm strict low carb and was NOT thrilled with the options (or lack thereof) available to me. There are sf desserts, such as cheesecake, brownies, and parfaits, but even those are LOADED with carbohydrates - so I would be skipping all desserts. Most appetizers are very unfriendly to low carbers as well. We're going to do Le Cellier, Crystal Palace, and Boma for our three TS meals - I feel I can find adequate lc selections there. For Counter Service I'll be splitting double cheeseburgers with dh and just having the cheese and burger patty -boring, I know, but it will do. That will help us spread the 3 days of DDP over our first four days, though (since we'll have it until midnight on checkout day). Cosmic Rays also has rotisserie chicken, which is probably injected with sugar, just our luck, but they tend to be fairly low carb nonetheless - just don't eat the skin, which probably has seasonings containing flour and maltodextrin.
I am SO relieved we dropped those other 7 days of the DDP. I was on the verge of a panic attack just thinking about it, and now I feel SO much better. Plus, we'll be moving to a huge 2 br timeshare for those 7 days, and I can eat all I want and KNOW what's in it.
Best lc friendly tip I've found was yesterday - first off, you can get FREE cups of ice water at any CS location. Second, you can decombo the meals - so if something comes with fries, you can ask for them to JUST charge you for the burger, chicken, etc. It will save you some money and reduce wasted food. Of course this is only if you're paying OOP.
Good luck with your decision. I agonized over it for weeks and finally came to the conclusion that DDP was just NOT for me. Add to that their crappy kids selections (I have a 5 and 7 year old), and that was that.