GWT does a great job reading UTF-8 encoded property files:

Both Constants and Messages use traditional Java properties files, with one notable difference: properties files used with GWT should be encoded as UTF-8 and may contain Unicode characters directly, avoiding the need for native2ascii.

This is nice, but there is a tiny little problem when using eclipse: the default encoding for java property files is ISO-8859-1.

This setting can be changed in the eclipse preferences:

Or you can change the encoding of a single file with “EDIT -> Set Encoding”…