As far as WDW is concerned, at the parks, WiFi is locked down -- they use it for the cash registers, but guests can't access it. The resorts do tend to have WiFi in the lobbies (that I think might be free), but most rooms at Disney Resorts provide HSIA via wired 10/100 ethernet for a fee (around $12/day I think, although I could be off there).
Edge access within the parks is spotty at best-- they limit the number of cell towers on property. Sometimes you get instant response, sometimes you can sit just waiting. A good bit of that I'm sure has to do with the number of people trying to piggyback onto the same towers though.
Off property, service is about what you'd expect-- Edge is fine, WiFi is as you find it (for pay at the "classier" hotels/resorts like the Hilton, free at the "cheaper" resorts like Hampton Inn). Several restaurants seem to offer free WiFi (like Denny's I believe), but these will tend to not be on Disney property.
I live in the area and am at WDW quite frequently (read every weekend or two).