Foxit PDF IFilter must be reinstalled after installing a software update or ... Microsoft Filter Pack
Hi,
Testing search in a development environment, I faced that after installation of MS Filter Pack you need to repair FoxIt ifilter installation. So it seems it behaves as a software update too ;)
By the way, they got a success story in Microsoft Exchange Hosted Services. Great!
Cheers!
P.S. it is documented at technet too