Microsoft report that they have added lots of new features to their mapping services, including the [partial] ability to import data in KML format.
“You can easily import data that you have on your computer into Collections. We support GeoRSS, GPX, and most flavors of KML.”
No matter what features they add I will not be using MS maps until the add the ability to export data in KML format. I tried MS maps when they first appeared and created several annotated maps. I soon stopped doing that because I found my data was locked in to the MS service.
I want the ability to move my data from one map service to another. Until MS stop locking in users and allow them to move their data around I am not interested in using any of their services.