Works well (edited for clarification) Rated 5 out of 5 stars
I just have some questions - what's the difference between 'Preserve scripts and source using "Save Complete"' and 'Take a faithful snapshot of the page'? Why is the MHTML checkbox available for both options, and what does it do exactly? As far as I can tell, both .maff and .mht are available after a Ctrl+S regardless, and the options (EDIT: by options I mean combinations of complete/snapshot and MHTML checked or not checked, not selecting a file extension) don't even seem to affect which extension is selected by default; it's always the last one used. Unrelated, but I like that you're getting rid of the "Add-on bar" and "Address bar" options under Interface, I don't see myself ever using them. "Address bar, for archived pages only" and "None" are the only two real options.This review is for a previous version of the add-on (22.214.171.124-signed).
The options you mentioned determine whether active content on the page is saved or not. Active content doesn't usually work correctly offline, thus the most useful option is the "snapshot", and it is the only save method available in the user interface of version 3.0.
Disabling the MHTML checkbox causes the add-on to create a legacy file format that is not supported by other browsers, and the option has also been removed starting from version 3.0.
If you're curious or would like a more detailed answer, you may follow the contact information on the support page at http://maf.mozdev.org/feedback.html.