Ever since the Profiles feature was first announced in the canary build I was excited, but it was limited (biggest limitation, these profiles weren’t saved) and the canary build was very unstable at the time. Eventually that early version moved into later builds, but the canary build updated further to allow saving those profiles for later use (making switching between different identities easy).
It would seem that the updated profiles (with the profile icon and saving the profiles for later) have now moved into the beta build, which I use on a day to day basis. I am really excited about this feature as I routinely have to use multiple accounts on various website throughout the day and it’s annoying to constantly have to sign out and sign back in to use it. This is especially true on google.com now that Google Apps for Domains accounts are full fledged google accounts. I have my company email account, my personal email account, and still another shared company account we use for certain things, and switching is quite annoying, especially if I forget which account I’m in.