Bulletins: Would be a great thing if it would post to the linked Teams as a new Bulletin is created. I know this can be done within Power Apps but in current state no one can use it ootb. The users would just not click on the new tab if they did not knew there was something new. So you can just continue adding a SharePoint page on a tab (which means you do not have to copy content to Bulletins and reach the same goal). So "could be a great tool, but not as is".
Milestones: That is a tool lots of our project guys were waiting for and I was excited as I read the news and began to try it. But sadly it turns out it is just a app with no connection to any Planner plan, just an island for data to be kept up to date by hand - that will not work for most people. So "high potential as well, but not as is".
I know I could put in some hours or days with Power Apps and modify both to be more connected. Sadly that is not what I have lots of time for.