Wasn't that behavior you describe after a new instance is saved changed back to be how it always was... ie. if the form is set to stay open after save of a new instance, then after save of a new instance all attribute values are cleared from the form and that instance is cleared from context, so that you will then be entering another new instance from scratch?
Pretty sure you can't save a new instance and (if the form remains open) have that instance remain in context with its attributes values remaining in the form, such that when the form is saved next it updates that instance. Though it would make sense to have this option in form settings, rather than have to FIND and VIEW the just-created instance.
The work-around to achieve exactly the behavior you want is to CREATE an instance and VIEW it when the user initiates entering a new instance. Have a 'clean-up' process which runs once a day to delete any dummy instances by using something like a 'CreatedTimestamp' attribute to serve as a flag.
The CreatedTimestamp value would not be set by the CREATE but would be updated during the first Save.
Then the clean-up process would delete all instances where CreatedTimestamp IS UNDEFINED (ie. new instances which were abandoned by users).
If the Object has mandatory attributes or rules invoked on creation, then you can use NO VALIDATION or NO RULES with CREATE to circumvent these so that the dummy instance creation can occur.
