MA House Rule 1: 40mm frontage bases. Non-negotiable. I know I can't use them in an MA tournament but you know what, MA should have realized that a great ebb & flow of 15mm gamers out there use 40mm.
MA House Rule 2: Group Combat Mechanic. Never liked this. One of the TMPers has a house rule that states losses must come from the fighting side rather than the back. Also that if a group is hit in the rear or flank those units hit must break off from the group and turn to face. I really like that.
Now that being said I've liked their shooting and movement rules since Mongoose first came out with them. Anyway I'll give it a good read and playtest this weekend and report my findings here. Also I want to be able to have a ruleset that I convert as easy as HOTT. I think MA can but I am not certain.