We've had a couple of recent cases that have come back to this and have found a great resource that the TMG (Threat Management Gateway) team had written regarding accessing CRM through IFD and page compression.  The link for the article is below and covers how to setup compression for sites being published through TMG.  CRM performance in many cases is driven by packet size and with CRM 2013 we are relying more on jscript for things like our command bar loads which can be a larger file than normal if left uncompressed. 

http://blogs.technet.com/b/isablog/archive/2011/08/05/slow-performance-accessing-crm-ifd-published-with-isa-tmg.aspx

I would be remiss if I didn't also give a shout out to the PFE team who put together a great article on compression and SSL for CRM and the impact it has for the system as a whole, that is linked below here. 

http://blogs.msdn.com/b/crminthefield/archive/2011/12/29/enable-wcf-compression-to-improve-crm-2011-network-performance.aspx