Please see the resources section for the code (Save Who.txt as Who.rdl). Support for an auto refresh interval of 90 seconds has also been added. I've also removed my copyright with my e-mail address from the bottom of the report :) Thanks!
1) Launch MS VSS or BIDS. Select File -> New -> File
2) Select XML File.
3) Paste the contents into the editor.
4) Save the file as Who.rdl in the following location: My Documents\SQL Server Management Studio\Custom Reports.
5) Connect to a database engine via the Management Studio UI, right-click the server name and select the custom reports option.
6) Select the Who.rdl file
Welcome additional comments/feedback at firstname.lastname@example.org