I just have to say something. I have no problem with anyone's preference, and I'm sure I won't change anyone's mind. My only issue is that off-site is being dismissed for reasons that really aren't very logical.
If you love staying on-site because that's your comfort level, I understand. If you just like the idea that you're actually staying at WDW, fine. But I see so many posts about transportation, and I really don't get it. I have a feeling a lot of it is the Disney marketing machine has worked. I have a feeling that off-site to many of you means I Driver, Kissimee, etc.
The resorts just off WDW property all have their own transportation. The better ones are just as reliable as Disney Transportation, and less crowded. So all the advantages of Disney transportation are really a myth.
Now...we have stayed on-site a few times and after the first couple times, we never used the transportation anymore. Standing in lines waiting to get on a bus with kids crying, packed to the gills, sometimes smelly, etc. is not Magic. Much, much easier to jump on a tram, takes you right to your car, and you drive back to your resort in peace- and usually get there before the bus. You return a much nicer room (at least compared to the mods and value.) Bottom line, I think many people make an emotional decision to stay on-site.
And for those of you who have been to WDW multiple times, don't you want to explore more than just WDW? When we go, it's 7-10 days. With a car, we can drive to the beaches, Cape Canaveral, Daytona, etc. And even if we don't, we at least drive around the area, outlet malls, restaurants, Universal Boardwalk, etc. There is so much more to see and do.