Not on mine. Clicking "Statistics" in the top right will tell you if it's still running in Legacy Mode or not. Once the servers are back up and running, CA will automatically switch back to appFeed mode. It just won't give you the same download failure message again as it's already got an up to date fall back saved.
EDIT: From a user perspective, there's very little difference between the two operating modes
Appfeed mode automatically grabs the latest lists. Legacy you have to redownload everything (and in the case of a server outage, switch to appfeed mode, then switch back to legacy mode)
Appfeed mode will display download totals and the baseOS for the various applications. Legacy mode will not
Appfeed mode grabs the lists in <10 seconds. Legacy mode may take a minute or so to download all the various files