I avoid EMHs at WDW, but I take advantage of MMs at DLR. (At DLR I stay off-site, so I wish I had more than one MM.)
Here is what others have said about the Exta Magic Hours (EMHs) at WDW. At WDW there are 30,000 on-site rooms. If each room has 3 Guests (at 90-percent occupancy) -- then 80,000 Guests have the
exclusive EMH benefit each day. There are people at WDW who love EMHs (although the lovers of WDW's EMHs will acknowledge that the morning EMH park tends to get very crowded, and they tend to parkhop to quieter places.) FWIW, TouringPlans.com, RideMax.com,
and TourGuideMike.com recommend avoiding EMHs at WDW.
As I understand it, DLR doesn't really advertise the MM perk to on-site Guests. I have heard that some CMs on the telephone really aren't up to speed about on-site Guests being able to go to MM on each morning that it's available. On-site guests at DLR are given some written information about MM when they check in, but it isn't heavily advertised like it is at WDW. (This way DLR, in the future, could change MM for on-site Guests, and there would be less disappointment.)
Also, at WDW each park has EMH about 1.5 or 2 times per week.
AT DLR, DL is the main park, and MM is offered 4 days per week.
From what I have heard, DL really isn't more crowded on Tuesdays and Thursdays due to MM days. (Saturdays and Sundays are more crowded, but that's because it's the weekend, and not because of MM.)
When you're eligible for the Magic Morning, I would
definitely take advantage of it. The general idea is to get to the DL entrance area at least 30 minutes early --although in the summer I would get there about 45 minutes early (but that's just my preference). I would recommend using MM for Fantasyland -- I would rather go to 6 FL attractions instead of using most of the time just for Finding Nemo. Another nice thing about MM is that at DL's regular opening time you are already inside DL, so you also get a head start. Also, the FP machines open at DL's regular opening time, so you have a great opportunity to get an early FP (with a shorter return time).
Here are 2 excellent threads about MM:
"Critique of MM/EE" by Hound 109
www.disboards.com/showthread.php?t=1392671
"Magic Morning (Early Entry) Super Thread" by DLR29
www.disboards.com/showthread.php?t=1675403
On Magic Morning days, when you don't have the privilege, I would avoid FL and TL, and start the day on the left side of DL.
Sorry for being so long.
Hope this helps.
P.S.: I see that Avalon451 already posted, so this post will be a little repetitive.