I really like the idea of being able to override edit/view. Currently it is very difficult to intermix fields from different regions of the Contact summary page (eg custom fields into core fieldsets, some core fields into custom field groups), which one of my clients thought was very important to help their users migrating from a legacy system. Also, would be very nice to be able to use profiles on the main contact / edit view rather than having all custom field groups and fields appear. As a default the latter might be fine, but sometimes it isn't appropriate.