HEADS UP! This article was written in 2007. Information provided might not be valid anymore and should be taken with a grain of salt.
In addition to compatibility changes new or improved options are:
data : string Alternative to postload and getload. Instead of fetching content from external resource it can be passed as parameter.
cancel : string Value for optional cancel button.
submit : string Empty value does not default to ‘OK’ anymore. If you want to have submit button you have to define this option.