The main con is, as mentioned above, the non-refundable nature of the reservation (and if you purchase insurance to cover it, you'll need "cancel for any reason" insurance, which generally must be purchased right away once you've booked -- I've been happy using Travel Guard in the past, although we only get insurance for a DVC rental when traveling with older family members with medical conditions, or if we're flying during snow season). Also, payment is due, in full, once your reservation is made. (This isn't a "con" necessarily, but something to be aware of.)
The DDP hasn't returned, so it's a moot point at present, but if it did, it's pretty simple to have the DVC member set it up for you ahead of time. If you're nervous about giving the member your CC number, you can purchase Disney gift cards in the needed amount, and give the member the gift card numbers instead. (*Tip: You can save even more by purchasing the gift cards for a discount at places like BJ's and Sam's Club, especially if you can stack the discount with credit card offers. I buy Disney gift cards at BJ's (for 4% off face value) using my Discover card, during the months of the year when Discover has a 5% cash back offer in effect for wholesale clubs, so I'm saving almost 9% on the gift cards themselves.) Also, as you're probably aware, if Disney comes out with a discount offer later for rooms or packages, you can't take advantage of it if you've already booked a room on DVC points. However, this isn't much of a "con" in my view, as the savings you enjoy by renting DVC points typically eclipses anything Disney is offering. We've rented DVC points for studios and 2-bedroom villas in the past, and have saved anywhere from 20-50% off of the rack rate for those same rooms.
We've booked DVC reservations through David's several times, and it's always been a seamless experience. Once a reservation is made, they'll send you the confirmation number, you link it to your My Disney Experience account like you would any other Disney resort reservation, and everything else, including dining reservations, etc., proceeds as normal. If you have questions or concerns, you can call or e-mail David's, and talk to a real, live, English-speaking, onsite employee. I've had to do so on a few occasions and they've been unfailingly patient and helpful.
Obviously you'll be buying your park tickets a la carte, and will need to link them to your account as well. If you haven't purchased tickets already, I recommend touringplans' ticket finder tool, which compares prices for several reputable third party resellers and direct from Disney, and tries different arrival dates, to suggest the best deal for your party.
https://touringplans.com/walt-disney-world/ticket-calculator
