The benefits of the update include upgrades for Android's voice search feature as well as security updates. Google did not provide a detailed list of changes and we are still waiting for an update on the Google Mobile blog.
There is a considerable number of users who report that the update may break Wi-Fi and USB tethering, while also not fixing the voice bug. The removal of the feature has not been confirmed by Google, but it appears that users who depend on tethering may want to hold off updating their phones until it is clear whether it is just a bug or if the feature has been removed. It is not a secret that both T-Mobile and AT&T are not crazy about this feature and would rather sell customers a separate tethering package.