<p>These days, more languages are using unicode, which is a good thing. But it also presents a danger. In the past there where troubles distinguising between 1 and l and 0 and O. But now we have a complete new range of similar characters.</p>

<p>For example:</p>

<pre><code>ì, î, ï, ı, ι, ί, ׀ ,أ ,آ, ỉ, ﺃ
</code></pre>

<p>With these, it is not that difficult to create some very hard to find bugs.</p>

<p>At my work, we have decided to stay with the ANSI characters for identifiers. Is there anybody out there using unicode identifiers and what are the experiences?</p>

Besides the similar character bugs you mention and the technical issues that might arise when using different editors (w/BOM, wo/BOM, different encodings in the same file by copy pasting which is only a problem when there are actually characters that cannot be encoded in ASCII and so on), I find that it's not worth using Unicode characters in identifiers. English has become the lingua franca of development and you should stick to it while writing code.
This I find particularly true for code that may be seen anywhere in the world by any developer (open source, or code that is sold along with the product).