A slow down on posts this week as we have been at the Association of Geographical Information 2006 conference presenting a paper on our use of Goolge Earth in Local Government. Of note, although sadly we missed the session on Google Earth due to other work, is that Google Earth is planning to include a 'Time Line' feature which should allow some level of animation.
ArcExplorer looks like its heading for a December release with full functionality based on a Arc backend server. So any GIS functions such as 'line of sight' etc seem to centre on you owning a ESRI server license. We assumed ArcExplorer would be GIS for the masses but if its only GIS as long as the data providers run a Arc server (?).
From talking to various data providers and users at the conference the consensus is that they also need to get some people to work on the look and feel of the user interface as at the moment its a bit clunky and does not compare well to Google Earth.
On a positive note about ArcExplorer though its looking like it will be released without any usage restrictions so companies and local government can use it free of charge. This is obviously not the case with the free version of Google Earth which is only for 'personal use'.