Oh yeah, that's a whole 'nother thing all together. Things that result in higher render times other than the obvious higher poly more object and reflection things: -High res textures (don't go higher than you can see on the screen, it's really not necessary unless you're looking to eventually print the thing and you know you're going to see it real up close) -Mixed materials, ESPECIALLY mixed water materials add render time as well, Eon actually recommended in a thread on their site that users not render in ultra when mixing water materials and using GI. -Soft shadows, they add a ton to the render time but in most scenes it is absolutely justified, especially as an enhancement to global ambiance scenes where you can't afford the render time bump up to Global Illumination. -Transparent objects (as tlaloc mentioned with the hair) are definate time crunchers, especially if you happen to try to mix them in with other materials (hence the previously mentioned water dilemma) -Anything with variable transparency or variable reflections is also going to be an additional time cruncher. Hope those tips help anybody trying to shave render time off, they're just things I've had to pay attention more and more to with me starting to get into animation at work.