The Closed Beta for Mirrors Edge Catalyst will begin on April 22nd. It will last for five days, ending on April 26th. Closed Beta participants will be able to try out several of the main missions in Faiths story, Side Missions, other optional content, and the Social Play features Mirrors Edge Catalyst has to offer. If you have been selected for the Closed Beta and you are a Frontrunner, you will receive an email with your code on April 22nd. Others who made it into the Closed Beta will receive their code on April 23rd.
http://www.mirrorsedge.com/frontrunner
I'll update the OP periodically.
Videos:
Opening Mission Gameplay (No Commentary)
Exploration Gameplay (No Commentary)
IGN playthrough
DICE explains Social Play
Impressions:
Eurogamer
Gamespot
Polygon