After reading a lot of HYPE regarding Jetpack, I am not very impressed. I had to resort to installing Dion Hulse's Core Control plug-in to disable the cURL just so I could connect to the WordPress.com site. I was getting errors regarding a none existent SSL Certificate.
The second major issue being with comment posts, it would be nice if it was a little more informative. Letting a person know that certain theme functions or hooks it relies upon exist or not. There was no direction information in the set-up which clearly expressed the theme requirement for this component.
The Social Networks for log-in are rather small and limited, without nice admin interface to control the order they are displayed in.
The facebook widget for the side panel was rather frustrating as well. It would break the display of additional widgets below or following it. I changed my themes around to test this behavior and sure enough, was broken on all of them I tested. I don't know what the cause of this problem was, don't care right now. I gave up messing around with JetPack. I've grown tired of having to hack so many other people's bad right now that it's not funny.