Magic Morning at DL worked fine for us on Thursday, 11/1, getting us on Peter Pan Flight in about 7 minutes after rope drop. In fairness, this was before they were ID checking everyone (they were only checking 4-5 day passholders, and we had 2-day passes). Also, it was before the Christmas parade filming, so the whole front of the castle was blocked off, and we had to walk around the right side of the castle to reach Fantasyland. That gave us a bit of an advantage over people who may not have known what to do, plus we had more room to maneuver (and more time to get past people who might have been more tired than we were).
After Peter Pan Flight, we rode Dumbo (just had to wait for the ride to cycle). For some reason Mr. Toad and Alice were down, so we tried the Teacups (had to wait for the ride to cycle), then back to Alice, then Toad, then Snow White, then Pinocchio, and finally a trip on Space Mountain before the park opened to everyone at 10. In short, we managed to do about as much as I've always done during a MM. (After that we hopped to DCA, which allowed us to get a FP for RSR, so I can't speak for DL crowds after the MM. I can't imagine they were much different than usual.)
DCA was a bit more of a mixed bag for us...we got in line before the gates opened for Early Entry (but not early enough!). By the time we got to RSR--no later than 8:15; probably closer to 8:10--there was a 60-minute wait! So our plan was to ride Luigi's that morning, but that wasn't open yet! At a bit of a loss, we went to Tower of Terror, which had a bit of a wait time, oddly, BECAUSE there was no one there. We ended up waiting for 2 other guests to join us, and then some other folks who I think had gone through some sort of other area and were waiting for one other member of their party by the elevator. Kind of weird. Anyway, once we were off ToT, we went back to Cars Land and Luigi's was open so we rode that with no problem. Then it was 8:40 and we figured it was time to head back to get in line for a FP for RSR, but we met Mater first.
I don't think Early Entry was a waste for DCA by any means, but if you're not near the front of the entrance line, you might have trouble getting onto RSR, and it might be helpful to have a couple backup plans in case your second choice ride isn't open either! I don't know if there's a perfect order to doing Cars Land, or if I was just too inexperienced.
If RSR is your priority, I currently would NOT avoid DCA on an Early Entry day. This hasn't been proven, but it looks to me like RSR may be more likely to be down for maintenance on non-Early Entry mornings than on Early Entry mornings. IF that is true (big if), you might actually have a better chance of getting a good Fastpass if you visited DCA on an Early Entry day, since if the ride opens at (for instance) noon, Fastpasses will be distributed with the first return time being noon instead of the park's opening time.
For the rest of Cars Land, Luigi's wait times are reported to be better than they were this summer, and Mater's wait time is usually reported as no more than 20 minutes (and if you like the music, it's a pretty fun queue anyway...I now realize a 20-minute wait was actually enjoyable!). I doubt Early Entry substantially affects much of anything else in DCA besides Cars Land and Toy Story Midway Mania. As Early Entry guests we found all the rest of Paradise Pier (except TSMM) to be walk-ons an hour after the park opened to all guests.