I think we blew it :) Vary: user-agent is not practical for correcting errant browser behavior.
For example; User-Agent: Mozilla/5.0 Gecko/20090729 Firefox/3.5.2 produces a myriad number of 'variant' flavors when tagging Vary with the User-Agent when determining if the deflate/gzip compression should be served, or the uncompressed variant. What we really meant to do was to determine which Accept-Encoding values were invalid based on known browser bugs, and -remove them- from the A-E header *prior* to determining the cache handling (quick handler hook) or typical content handling. Which implies that setenvif + headers need an extra chance to run really first in front of the quick handler. Any better suggestions?
