The functionalities (especially the bookmarks while logged into your Google account) look nice.
It collects some info (why does every toolbar try to change your default home page and your default error page? - so annoying), but as it's opt in - its your choice to have a Google toolbar/account - I'm not too concerned about that aspect.
However - if you regularly login to several AdWords accounts its essentially useless.
I don't want to connect my bookmarks/GMail/start page to a corporate Google account. To access these features, I have to logout of the corporate account into my personal account - which them means I can't access any AdWords accounts as it automatically logs me into the new Google account.
I could leave multiple browsers open, each logged into its own Google account, but that would be a pain as I try to navigate between different browsers and tabs (I'm an Avant browser user).
Until Google finds a way to have a 'Google account manager' login where one can set permissions across multiple Google accounts (including analytics, adwords, adsense, gmail, etc), allow access to multiple Google accounts at the same time (one corporate, one personal) - etc - I don't see how anyone working for an advertising agency (or even anyone who logs into a business AdWords account) could ever embrace any of these features.