AnalyzeMoveRequestStats.ps1 can be used to analyze the performance of a batch of move requests to identify reasons for slower performance.

The script provides important performance statistics from a given set of move request statistics. It also generates two files - one for the failure list, and one for individual move statistics. The files can then be analyzed to identify problems that you might be seeing during mailbox moves.

The script goes with the following blog post:

http://blogs.technet.com/b/exchange/archive/2014/03/24/mailbox-migration-performance-analysis.aspx

Update 9/16/2014: Updated the script to work on mailboxes larger than 2GB.