Decentralized - there is no central authority over bitcoin.

No one can print more bitcoins when the limit of 21mil is hit.
No one can stop you from sending your bitcoins to someone else (wikileaks being a popular example)
No ridiculous fee's (other than 1 cent or whatever (believe it's even lower) for transaction fee) for sending someone money.

There isn't really any big advantage for the regular person other than that there's basically no fee's.

Pretty sure there are other reasons to use bitcoins, but those 3 are probably the most important things.