I was a beta tester as well. All the reasons you listed apply. Even before they opened for the masses I have moved all my domains in. Some extra reasons:
- Simple integration if you are on Google apps (I am grandfathered, using their, old, standard, free Gapps.
- Customer support was superb and instant, via chat, and it was great. The person knew what he was doing.
- Unlike other domain sellers, Google Domains is NOT trying to sell me anything other than domains.
- Canceling is easy! I don't have to wait in calls with 1&1!
- Customer support was great. They get back to me after an hour if I email and if I call, responses are very fast.
- User interface is clean and clear.