Project was dead for a while, but running into problems made me patch it a little.
Regression bug fixed: Double arrays created natively in Matlab are read incorrectly (reversed byte ordering)
The new JMatIO package is available for download. The changes: performance, junit tests, some changes in API.
From now on, only SVN will be supported.
First alpha version of JMatIO was released with a project start. I may improve this library as I need it in some of my projects :) I do hope it will be helpful if you ever feel the need of saving some data to MAT-file in your JAVA application.