Hi Sohaib -
I'm not 100% clear what you're doing, but it sounds like you're trying a simple tabcmd get "/workbooks/<workbook>"?
Each time you launch tabcmd there will be a generally be a pause as the JVM gets spun up. After that, things should go pretty quickly. I just ran the following as a test, and got my workbook in ~5.6 seconds...might it be the user's machine is under-powered?:
C:\>tabcmd get "/workbooks/Book2.twbx" -f c:\book2.twbx -s http://localhost -u username -p password
If your workbooks are big .twbx files because they contain large data extracts, you may be experiencing problems with both the file transfer and the cost of unzipping the .twbx ZIP file format to get the workbook XML within. You may wish to consider using a non-extract data source such as a live database connection, or alternatively a Data Server connection with its own data extract. This will ensure that you aren't bringing down large data extracts with your packaged workbooks, and this may address most of your performance problems.
I hope this helps,