I think this is such a beautiful name. I would probably would use it if it weren't for the hard spelling and pronunciation. A clearer spelling like Evann just doesn't have the same charm to it.
The name is quite a difficulty for anyone outside of Ireland. For one that uses the pronunciation (see comment above) "AY ven," go with Aven. It's short, sweet and won't have the problems that Aoibheann would.
I love this name! I love the meaning, the pronunciation, the fact that it's Irish and I would absolutely name my daughter this. Who cares if the wonderful spelling will break her teachers' necks?!