I don't find this really worth upgrading from my 920 and to be honest, I feels 920 is still considered a good WP8 phone to get for a new buyer except the availability is an issue.

Few things that really need to consider IMO;
-lack of glance support
-no cyan/yellow back cover
-no expandable storage
-lack of assertive display

which in short; 5" version of 1520 then I'll be really happy to upgrade