Sam from OhNuts informed me that Google is having some major issues with Google Base feeds. Google Base feeds are used to send data from your site to Google Product Search, amongst other places.
A Google Groups announcement thread says the issue will slow down the normal time it takes for your updates to be seen on Google Base and Google Product Search results. There is nothing a webmaster can do here but wait for Google to fix the issue. So do not bother resubmitting your feed, cause it won't help.
Google did fix the processing delay for smaller feeds, but feeds that are larger than 1 MB are still affected. The Google Base Guy, the official Google representative, said:
Thanks again for your patience and I will get back to you with more updates.
Forum discussion at Google Groups.
Update: On December 1st, Google has fixed the issue completely.