Just to chime in... the line of sight, vision, and lighting settings are one thing that can change your gameplay just a bit. While you can ignore them all (pretty much any feature in MT is setup to be turned off), it's really fun to have your players exploring a dungeon by torchlight and have the line of sight and light system work automatically. Rounding a corner and then having a bunch of zombies revealed w/o you as a DM messing with it or have them see the light at the end of the hallway and wonder what is beyond it can be pretty fun.
Yeah, you can narrate everything and create the same feel, but initially it'll be enough of a shift that it'll be enjoyable!