We just booked our trip a couple of weeks ago for the end of September. We were originally looking at staying onsite and only doing 5 days because it's SO expensive. After a lot of research, we booked a 4 bedroom, 3.5 bathroom villa about 15 minutes away from MK, at $806 total for 9 nights, including taxes, cleaning, resort fees, and everything. We'll have a full kitchen, free Wi-Fi, full washer and dryer, access to the resort amenities, including a couple of pools with water slides and a lazy river, etc.
There are six of us going, 3 adults and 3 kids, and we needed five separate beds in at least 3 separate bedrooms, one of which had to be a king size to accommodate my 6' 5" husband. Staying onsite, there was just no way to do that without spending an absolute fortune. We'd have had to get either a huge villa at a deluxe resort, or two or three rooms or suites at a moderate or value resort. At a minimum, it would have cost us triple what we're paying, and we still wouldn't have had the full kitchen, laundry facilities, or anywhere near the amount of space.
In terms of transportation, we used Disney transportation when we went several years ago, and there's no way I'm doing that again, so we'd have wanted to rent a car anyway, even if we stayed onsite. We're renting a minivan for 9 days, for $345. Even adding in car rental, parking fees, gas, and tolls, we're still saving a ton over the cost of staying onsite.
Obviously we haven't actually taken our trip yet, but at this point, I'm very happy with the decision. I was a little bummed at not being right in the middle of the "magic", but now we can stay almost twice as long and be more comfortable while we're there, which should make up for it!
We're renting the villa form a private owner, and it's in Regal Palms. We found it through either
www.homeaway.com or
www.vacationrentals.com, I can't recall which. Many of the same properties are listed on both of those sites by the owners.