We picked up a Champion brand safe from our local distributor for my FIL, and, being a lover of locks, safes and nonsense like that all my life, I went poking around the warehouse...
Some punk kids worked on this safe for 6 hours and never got it open. That is not to say they were skilled (or sober/straight) but it's the story I got from the dealer.
I always figure it's a law of averages. If someone is determined and knowledgeable, they can breech my safe and get my goodies. Hopefully they will be in a hurry and miss it, or decide it's not worth their time (they are too busy tearing my TV off the wall and packing my stereo up with the silverware.)