Google Hangouts with SMS integration is finally hitting the Play Store, and it is a slightly higher version than that was pulled from the Nexus 5. If you have not gotten the new apk, you can probably just go into the Play Store and download it when made available for your device.
Not only was SMS integration been added to this version, but GIF animations, and location sharing was added as well. Makes the whole messaging experience just a little better for the user. Being that it is an increment up from the apk we had, it probably just has some performance enhancements and bug fixes. So head to the Play Store and get it on your device. Tell how you like it.