I imagine it's not very important to many of you, but for my site, Google Images is quite significant. I noticed an update yesterday of images for the first time in many months. It looks like they actually just switched out the servers and changed the DNS entry, so whether you see the update is determined by whether the DNS has propagated to you. Old servers: 216.239.39.104, 216.239.39.99 New servers: 64.233.167.104, 64.233.167.99, 64.233.167.147 If you want to try out the different servers and compare, construct a query like this and swap out the IPs: http://216.239.39.104/images?q=periodic+table
It is just another type of search, so this doesn't deserve to be called update. I see "similar sites" update.
It seems that the old servers have more search results. That's probably why you see different results.