I'm not sure Cortana is really a Siri or Google Now beater. I think a lot of people don't seem to understand what Siri or Google Now can do. For example, Siri is totally contextual and can pull details out of text messages and emails, and Google Now already has a notebook with all the info it has on you. So I'm not sure why the notebook is so innovative. It's not. The only couple things that are new are the fact that you can integrate apps into it. This was available in WP8 but was never used to it's full extent, and I don't expect WP8.1 to be much better in that regard. Also, being able to remind based on triggers like a phone call might be new. But I'm not sure. Lastly, being able to say first one, last one, second one, looks like it's new too.
In any case, it looks cool, and it combines the best of Siri and Google Now, but I wouldn't call any of it innovative. I'm a big WP ****** and when I was showing off what Cortana could do based off of the earlier leaks to my Apple fanboys, they were able to do all of the same things including getting flight info, time to work, traffic, stocks, weather, etc.... So maybe someone can educate me as to what Cortana can do that is so innovative?
Thanks!