In '06 we stayed for 7 nights at Pop Century. We loved it and I thought that would be our "Disney Home." Then this past May '08 we took a 10 day trip because we wanted to do Universal Studios & Islands of Adventure. Having to take a paid shuttle bus or rent a car from Disney for 3 days to get to the other parks was going to cost as much as a 10 day pre-paid rental through Priceline ($12 per day). So, that got me to thinking about staying off-site since we'd already have a rental.
We stayed at Windsor Hills and LOVED IT!!! That will be our new home when we go back. I doubt I'll ever stay on-site again unless it's just DH and I when the kids are grown and gone.
Advantage:
1) Lots of room -- The kids had their own bedrooms w/ TVs & DVDs, a playstation w/games, and we had two bathrooms and a washer/dryer right in the condo. We also had a nice balcony to sit out on in the mornings while we ate breakfast. Four of us in a value resort tiny room for 10 days would have been torture!
2) It took us literally 15 minutes from the moment we pulled out of our parking space at Windsor Hills until we were entering the front gates at the parks during the Memorial holiday. It's really a five minute drive to the parks from Windsor Hills. The one park that took the longest was Magic Kingdom because you have park at the transportation center and then take the monorail or a ferry after that.
3) We all agree that we were able to get back to the condo faster driving ourselves than we did staying on-site and waiting for a bus.
4)The pool at Windsor Hills had a really cool slide which was a big plus for the kids. The pools at the value resorts don't have slides.
5) We bought breakfast food and ate breakfast in the condo each morning which saved us quite a bit.
6) We ate lunch at the parks each day and had most of our dinners off-site. We still had great meals at a fraction of what we'd have paid for sit down places in Disney. We still did a couple of our favorite places, but we were happy with eating off-site, too!
7) DS got pneumonia on our trip. He was sick the last 4 days, so it was really nice having his own room to be in since he was coughing up a storm.
8) We had free high-speed wireless internet which we couldn't get at Pop Century.
9) Windsor Hills was $85 per night vs Pop Century at $109 for weekdays, $119 for weekend nights and $124 for the Memorial Day holiday. In October, the rates will be less at both places.
Disadvantage:
1) If you've never been to Disney and stayed on-site, I'd say that it's important to have that experience. Once you've experienced it though, it's just as magical not staying on-site.
2) We had to pay $11 per day for parking and we had to pay for gas and for the rental car. It was basically a wash though due to the cheaper rate at Windsor Hills.
3) You cannot get the dining plan if you stay off-site.
4) If you arrive late, check in can be more difficult at WH since each unit is owned individually. Look for owners who have lock boxes so you don't have to drive to their office somewhere to pick up the keys. Since we arrived after midnight, our owner gave us the lock box code so we didn't have to drive to a separate office.
5) No daily maid service at the condo, so you have to run the dishwasher, etc... We also had to provide our own trash bags and paper towels. We were also only provided with one roll of toilet paper per bathroom, so we had to buy more. This could vary from one owner to the next, so make sure to ask what is provided and what isn't.
6) No EMH if you stay off-site. We always make it a point to avoid EMH parks because that park is the most crowded, but that shouldn't be a factor if you are going in October. In May & early June, the parks were open until 10:00 or midnight on some nights, so we didn't need the EMH anyways. In October, the parks close earlier, so that would be something to consider.