In the non-beta version, after I add an address to a building it gets a little building icon on it. That lets me know that I've updated the address for that building.

Thanks for reporting - I didn't realize that the icon was showing for tagged buildings and missing for plain buildings. I kind of thought that showing the icon was a bug, and didn't realize anyone was using it as signal that the building might have an address.

Maybe instead of adding the icon back, we could find a better way to show the building's address housenumber at high zooms?

There is some previous discussion on this iD issue about showing more icons/colors for buildings - I'd still prefer to keep the interface clean and simple if we can.

It wasn't very messy with that building icon showing the way it did before. I was real handy for me to come back to a neighborhood and see where I left off without having to select the building and see whether it had an address attribute. Around zoom level 19 and above would be useable.

Maybe display the house number at zoom level 19 and above if you want to do something different than an icon.

BTW, from my perspective I'd say this is a "must have". Without a way to quickly identify which buildings have addresses already, it would just be too many clicks and checks to make sure I don't mess things up or forget something.