From the Google Earth blog:
Esri has just released version one of ArcGIS Earth, a Google Earth like 3D globe for the desktop. It is not really a Google Earth competitor, as it is targeted at the professional GIS user. Google Earth has historically been used by both professional GIS users and casual users, with Google Earth Pro aimed more at the professional GIS user. In early 2015 Google announced they would be discontinuing their enterprise GIS products, Google Earth Enterprise and Google Maps Engine and at the same time made Google Earth Pro free. Wementioned at the time that they appeared to be assisting their customers to transition to Esri products.
We wouldn’t really recommend ArcGIS Earth for the casual user, but there is no harm in trying it out. For the professional GIS user it is definitely worth a look. It is currently only available for Windows (version 7 and above). You can download it here. It does require you to enter an email address, organization (optional) and industry (you can use ‘civilian’ if it is for non-professional use), but other than that the software is free and easy to install.
As far as we can tell, it has no ‘historical imagery’ feature and the imagery transitions between several different sets as you zoom in. There is no indication on screen as to the age or origin of the imagery.
A view of the Swiss Alps in ArcGIS Earth.
The same location as above in Google Earth.
One feature we found interesting is the ability to show completely different global datasets, including the more traditional map type views. This is something Google Earth lacks.
It appears to have good support for KML, so you can easily copy placemarks between it and Google Earth.
It is only version one so we expect it to improve significantly with time.