<p>I work on a lot of Asian Language localization projects, and am looking for a powerful text editor with the following features:</p>

<p>1) Unicode support
2) Find in Files
3) Replace in Files
4) Regular expressions
5) Multiline find/replace
6) Built-in diff</p>

<p>I am currently using NotePad++, but it doesn't really support unicode in its find-in-files tool, which is a deal-breaker. EmEditor looks promising, but it doesn't have multi-line find/replace. </p>

<p>Anyone working with Chinese, Japanese, or Korean files have a text editor that they like, free or commercial?</p>

Ultraedit
is my favorite text editor and it is advertised as having good Unicode support
http://www.ultraedit.com/support/tutorials_power_tips/ultraedit/unicode.html
.
It has the find / replace / regex features you're looking for as well as almost every other feature I have ever needed.