Aside from the coolness of these extensions, this is a very good business strategy. Chrome is becoming an enhancer to Google web applications. Users would be more likely to use Google web apps if they use Chrome. If they use Google web apps aggressively already, then they are making users to choose Chrome over other browsers. This is definitely something Microsoft's IE is lacking.
I like the new Google Calendar extension, but I think it would've been nice if they had integrated the functionality of the Calendar Checker in to the new one. I like the badge that pops up displaying just how many days/hours are left until my next appointment rather than having to click to check myself.
It is open source so I'm sure it will get added soon.