Here it is guys!

OPENCART 1.5.1.3

You can download it here:

http://opencart.googlecode.com/files/opencart_v1.5.1.3.zip

If there are any bugs you can post them in this thread:
http://forum.opencart.com/viewtopic.php?f=161&t=42226

Updated the tax system added new functionality to cope with new laws bought about by the US and EU.
Taxes can also be assigned to different customer groups
Added auto complete in the admin for search for products, orders, customers, etc..
Added new payment gateway called Web Payment Software

FIXED:
Added utf-8 helper functions so there is no need for mb extension to be installed.
Page speed rendering issue IE
Multi-Store Layout Change not working for second store

Please refer to  the bug tracker list for all the fixes done:

http://code.google.com/p/opencart/issues/list?can=1&q=&colspec=ID%20Type%20Status%20Priority%20Milestone%20Owner%20Summary

Enjoy!