Played some more last night - love the idea of the combat arena, the whole 'gameshow' presentation of it. Good customization around it as well. Had a couple of quick goes, got two silver awards so unlocked the Reaper units and Elites.
Went to the arcade and played some of the mini-games, didn't realize that there were so many! Won a load of music tracks and a plushie for the apartment.
Ended up going back to the Normandy, progressing my next mission, which was the Geth Dreadnaught, and then had a load more hookups unlock via email.