I did the add-on through
ABD after my Knights & Lights trip this past summer. It was on the expensive side, but I felt that the perks were worth it to have everything included. The biggest perks were the pre-arranged transportation to DLP from Paris then from DLP to the airport, and the VIP FastPass. I chose the stay at Hotel NY, which was a bit less expensive than the option to stay at the Disneyland Hotel. The Disneyland Hotel has it own perks, such as overlooking the park, but I found the walk to and from Hotel NY through the Disney Village wasn't that far and was very nice.
I only did the 2 night option, which included a 3-day park hopper. But with the VIP FastPass, which I think is only otherwise available if you are staying concierge, I was able to get on those rides without any wait - just go up to the FastPass line and show them your pass. The CM's at the FP entrance always seemed to be impressed when they saw my pass. I also took advantage of the morning extra magic hours at Disneyland Park on my full day and was able to see everything I wanted in that day and a half.
I'm sure there are less expensive ways to do DLP booking on your own, but I felt this was easiest and just wanted to stay with the ABD service for the whole trip.