1. Clicking sign up button from an invitation opens modal dialog with basic information form. A preview area updates your info as you fill out the form.
2. The birthday input filters and corrects date format. City/State shows suggestions, although I think the first one in this example isn't a valid suggestion.
3. A conditional select is shown for neighborhoods matching my city.
4. Following entry of email/password, additional fields are disclosed in the dialog.
5. Confirmation dialog is displayed.