It appears Google really doesn't want to leave any stone unturned when it comes to easing its own apps into material design (no matter how long it may take). The latest to get an incremental refresh is Google Opinion Rewards - the app has been updated with a revised launcher icon (seen in the thumbnail for this post), and a new toolbar inside the app. The icon is a bit closer to material, but doesn't carry the exact same use of shadows as Google's other recent updates.
The card structure and every other component of the interface appears to be the same, but the new toolbar/status bar theming is nice to see.
before and after
Now, if I could just get a few more surveys.
The APK is signed by Google and upgrades your existing app. The cryptographic signature guarantees that the file is safe to install and was not tampered with in any way. Rather than wait for Google to push this download to your devices, which can take days, download and install it just like any other APK.
File name: com.google.android.apps.paidtasks-20141202-41-minAPI10.apk
Version: 20141202 (41)