Well, on the subject of house killing, about the only time I kill houses as a primary target is when I tool rush with axers. Some things one should bear in mind about killing houses.
1. If your killng lots of peons, then killing houses will have little effect as his pop is dropping so fast that he can still build military units.
2. If you can get a person up against their housing limit, it can be devasting to them, but its not easy, nor does it tend to last long.
When axer rushing, the primary goals for me is to force my opponant to relocate, which costs wood, to destroy my opponants tc, which costs wood to replace and seriously delay's bronze, to kill my opponants market/tool buildings, forcing my opponant to rebuild these buildings to bronze, which costs wood, and to destroy houses, which can delay an tool response on me, and costs wood to replace. Rarely do I get many peons, as most opponants I play are smart enough to run, thus its not my goal with an axer rush, my goal is to starve him off wood, I locate his new pit/tc and continuing destroying, I have destroyed a 4 tc's of an opponant while they languised in tool with hoardes of food and no ability to do anything. Also if your costing your opponant alot of wood, taking the sea's and sinking his fleet tends to be easier.
basicily, the primary goal of an axer rush is to overextend my opponants need for wood, thus breaking his economy to the point where it cant function, and killing houses is an important aspect of this. And, as I am leaving most of his peons alive, he wlil more likely hit the pop limit with his houses destroyed, thus any response he wishes to make, through either rushing me or defending his buildings will be delayed
Otherwise I would rather destroy military buildings, tc, farms, etc before houses.