Alternatively, if you are ever in Scotland it is widely used and understood as a synonym for yes. In fact, I often use it myself.

If you use "aye", you would need to adopt the other conventions that go with it (eg. using "nay" for "no", etc). It wouldn't work as a substitute by itself. For example: Q: "Are you managing work OK?" A: "Aye, I'm managing it very well, thankyou." --> Too strange! "Aye" is out-of-place here, against the regular polite English. A better (pirate!) answer is: "Aye, that I be. 'Tis a task safe within me humble abilities, thankin' ye." Don't forget the accent. ;)

It is part of the way that English speakers portray pirates. It is how a pirate says yes. The navy also uses it in the phrase "aye aye sir." So I see it as a way of saying yes on boats, yet it can still be used in normal conversation, but it will make you sound like a pirate, a Scottish person, or a person from history.

aye = yea i use it with my friends =) we are old-fashioned dudes

Aye is a very old fashioned term meaning yes. No I would not use it unless you were an actor in a pirate movie.