That's kind of what I'm trying to figure out right now, actually. This will only be my second D&D campaign that I've DM'd, and the last time I allowed the players to get way too powerful in ways that were... well... broken and difficult. I will not make that mistake again, and I want to be a whole lot harder on them than I was last time. I'm also very big on the character-driven stuff - real roleplaying above dungeon crawls.
But because of the last campaign, me being "tougher" on them probably won't be as tough as you are on your characters.
I think I will have to experiment a little bit to get it right... Even if I don't do 3 per session, I do like the idea of action points on a steady basis, as opposed to the 5 + 1/2 level each time you level. That rule just doesn't quite sit right with me.