We have have rented 2 townhouses, a condo, and a 5-bedroom house (same place twice) in Windsor Hills, and a townhouse in Windsor Palms. Six rentals so far, and nothing but positive experiences every time! We are looking forward to our 7th rental through vrbo in Nov 2012!
Why do we like it so much? It is very personal, and the owners we have dealt with have been super-helpful, answering questions about the rental units, resorts and area in general. We have only used vrbo for WDW vacations to date, but every time I dream of going elsewhere, vrbo is the FIRST place I check for potential accommodations.
BTW - we LOVE Windsor Hills! At this point, it would take something like an almost-free suite at a luxury WDW resort to coax me away from the joys of staying in a vacation home in Windsor Hills. I hope your MIL will take a leap of faith and that your rental experience will be as wonderful as ours to date!