I know all the books say Ush-een (which I don't like - sounds like a girls name to me) but I've known a couple of people with the name who pronounce it Osh-in - which I love!
DH is Irish and pronounces it the first way but agrees with me that he loves it the second way. All our family is in Ireland (though they will pronounce it the way we tell them!) but we live abroad (in a very international community) and our son is likely to not be living in Ireland as well. DS1 also has an Irish name that is pronounced slightly differently than it is spelt (though much closer and it wasn't intentional!) and it's never been a problem.
So how would you pronounce it? If you wanted it to be Osh-in, how would you spell it? Or are we just storing up problems for ourselves and DS?? We're really struggling with other names we agree on!