Little-fizz is right about the dead spots. This is a major safety note- if you don't regularly stir up sand it will develop anaerobic pockets which, if released into the aquarium, can be really, really bad for your fish.
Having said that, I used sand and I love it! Plus, play sand at home depot runs $4/50 lbs, so it's definitely a cheap way to go. It's perfectly tank safe, just make sure you rinse it like crazy. Once you put it in it will initially fog up your aquarium regardless of the endless rinsing you can do, but the rinsing does help.