Received my signed Collector's Edition box (with signed guidebook), t-shirt, post card and mouse pad via postal delivery today (April 2/2015). Annoying that the mail carrier just left the box on my door step because no one was home at the time, but that's an issue with our post office (Toronto, Canada).
Paradox Interactive had previously sent me an email on March 26/2015, notifying me that the items had shipped via USPS with an estimated delivery date of April 3rd to April 9th, so everything actually arrived a day early.