Running it on 1320. Sometimes froze when leaving store. Had issues with Cortana. I've now worked through these issues. It now runs really well!
A word of advice for the 1320. DO NOT RESTORE A BACK UP. It creates havoc! All sorts of crashes, lock ups, screen freeze yet phone works (?????), etc.
So, completely vanilla install. DO NOT RESTORE. HARD RESET. Don't put MSN news / weather on the start screen along with Cortana. Cortana's live tile will stop. Sometimes Cortana takes a while to read texts. Not sure about Skype, I don't use it. When system apps are updating in store, you WILL get some unable to install etc.....Touch won't install on the 1320, but glance does ( and it looks good ). Here maps can fail but retry and it'll work.
I've not noticed a lot of difference speed wise between the 1320 and my 640xl. Quad core processors only really come into their own with 'heavy' processing. Most of the time only one or two cores operate, unless you have hundreds of tabs open or are running 'heavy' gaming. With the 1320 running at 1.7ghz dual core, the OS isn't going to cause to much of an issue, unless you have power hungry apps running, and that's where any multiple core falls down because they are throttled by the ram available, and the heat generated.
Anyways, hope that helps. I love it on the large screen