So finally, finally a name is truly jumping out at me (yay).
I bet you would get the correct pronunciation from most people. Some people will get it wrong, though, but I bet not enough to let the name go over. People are familiar with Niles, so they would probably assume a long 'i" sound from the looks of it. I am happy that you have found something that you are excited about. Congrats!
I love the name Niall! Great choice. I do think he'll have to do a bit of pronunciation-correcting, but he'll live. :)
My name is Kristine and have spent my life saying:
I love it!
Welcoming a bonus baby #3 February 2011!
My first thought pronouncing it was
I've always thought it was 'nye-ul'. I really like it!