We have stayed many times at WBC. Both in presidentials and deluxe. The presidentials are gorgeous with lots of heavy, dark furniture and stainless steel appliances but the deluxe are just as comfortable! We book through ebay every time and have never had a bad experience. We have bought from timetogovacation, theroseofsharon, pen-management, lcwindy, farrells vacations, and many others. No problems ever. The first few times I called ahead to make sure Bonnet Creek had our reservation because I was nervous about the process but it has always gone smoothly.
Have booked presidential units 3-4 times from Ken Price with vacation upgrades. The units are great, seem to be more square footage, and have been available but are more costly. Still a wonderful alternative to a Disney room.
Stayed in a 4 BR Presidential in 2014, booked through Vacation Strategies (didn't have enough of my own Wyndham Points at that time) but have stayed non presidential many many times. Was the 4BR Pres amazing? Oh Absolutely! But honestly the non pres are great too. If it's not a huge difference in price then I say go for it, enjoy the experience... We booked ours 5 weeks before our trip, but keep in mind this was 4 years ago.