I stand corrected on the pronunciation of "gyros". Sorry about that; I have a friend who insists that the pronunciation "HEE-ro" is correct, and up to now I haven't done any research to verify or dispute that. But this thread has prompted me to delve into the subject, at least far enough to come up with a couple of web-pages about it:

An article entitled "Just How Do You Pronounce Gyros, Anyway? And is The Gosh-Darned Word Plural, or Singular?" (http://users.erols.com/textuscs/gyros/justhow.html)

A restaurant review, complete with pronunciation of the name (http://www.louisvillehotbites.com/omar.shtml)

And here's an excerpt from a Scherzi & Sospiri column entitled "More Songs About Squiggles and Sounds" (http://www.inu.org/scherzi/200101/entry5.htm):

Every time I go to order a gyro from a sandwich store, I have to decide whether to pronounce it the way my mother, a native speaker of Greek, pronounced it, or pronounce it like "jy-row" (if umlauts are tricky, I'm not even going to attempt IPA).

The Greek gamma is pronounced further back in the throat than the English g. Before certain vowels (typically ones pronounced in the back of the mouth), gamma sounds a lot like a g, but maybe with some gargling. Before other vowels (typically ones pronounced in the front of the mouth), it sounds more like a y, but maybe with a little buzzing. The upsilon in gyro, transliterated as y, and pronounced in Modern Greek as "ee" is one of the front vowels that make gamma sound more like a y.

Once I went up to the counter at the Great Wraps that used to be at the Cambridgeside Galleria and asked for a "yeero" (rolled r and all) and was met with a blank stare. After I asked for a "jyrow" I was understood. I was handed a sandwich whose proximity to gyrohood was consistent with its pronunciation.

Readers who are familiar with my non-confrontational methods will not be surprised to know that although I love those peculiar lamb sandwiches, I will not order them aloud. In fact, I have avoided asking for gyros for many years longer than I've avoided Münster. There is such a thing as knowing too much for one's own good.