PvZ - Lessons in Harassment and Pushes

I just played a whole bunch of games against my Protoss buddy, and here's what we learned:

1. An early push of 2-3 Zealots from a 2-Gate opening forces Spine Crawlers or Zerglings.  However, it really doesn't do anything for the Protoss player, either - he ends up sacrificing economy to force defenses instead of Drones.
2. If the Zerg player doesn't block his/her ramp and makes spine crawlers at the natural expansion, it's plenty easy to march your zealots right past everything and attack the main.
3. A Zerg player can almost always get away with a hatch-first build on the newer, larger maps.  However, defending wide-open expansions with spine crawlers is a bad idea.
4. The Protoss mid-game army really should include Colossi, even against Roach.  Colossi do SO much damage their splash effect that they are really worthwhile, and unlike High Templar, they don't run out of energy.  Immortals are good, but if the savvy Zerg player brings in Zerglings from behind, Immortals / Stalkers get trounced pretty badly.