If you are using Google Checkout and/or Google Website Optimizer we recommend you upgrade to this latest version as there were some bug fixes related to these modules.
A Diff file between Magento version 126.96.36.199 and 188.8.131.52 is available here.
Note: We do NOT recommend upgrading a production installation of Magento directly. Please backup database and all files before upgrading. Please make sure to check file permission before trying to upgrade through your Magento Connect Manager.