According to bartleby.com:
This 17th-century borrowing from French has traditionally been pronounced (nch), rhyming with itch. The pronunciation (nsh), rhyming with quiche, is a 20th-century revival of the French pronunciation, which some people dislike because they think it seems affected.
So, what about you? Do you say "nitch" or "neesh"? Add a comment or vote in the poll on the right.