I’ve added the opt-in links to the Google Play BETA. Feel free to participate, or not. The choice is yours but, whenever there are updates, I always release them to the BETA users first.
You’ll need to own the respective application and then sign-in with the Google account you downloaded/purchased it with.
Also, once you become a BETA tester, you can’t seem to write a review anymore. The system only lets you leave private feedback at that point, so don’t forget to leave a 5-star review before joining. =)