I have one. I keep a usb key that stores encryption keys in it along with some cash. I may also start storing monthly computer backups in it, just in case. Oh and my birth certificate and SIN card. If there's ever a fire and I lose all my ID, it'll make things a hell of a lot easier.
I don't have any personal input, but at the watch forums I frequent, everyone who has a "special-occasion" watch (read: costs more than your car) keep it in a safe deposit box, not at their house. The retrieve them on the way home from work, or bring them home to take pictures...then back to the box.
Its where I keep my pistol, in-ear broadband police radio, ASP Baton, fake passports and ID's, $50k in USD, CNY, and EUR, as well as 2.5million dollars in non-traceable rough diamonds, a quick disguise, and a vial of hydrochloric acid to dispose of anything I brought with me into the safe room that I cannot take out. Oh, and some baseball cards.
I hate them, i have to open them for people all the time when im at work. I think its way cooler and smarter to just hide things in your walls or under your carpets etc. since it's not like the things you keep in the boxes are insured anyways. you can always access your hiding places in your home whenever you want to bot just during bank hours.