I just tried it. I copied a paragraph from Pages and was able to successfully paste it into Notes, Safari, Dictionary (3rd party app), even in Epicurious's searh field without any problems. I don't know why you should have any issues.
Hm... It wouldn't let me paste into the Wordpress app, or directly into a new email message, or into the browser based Wordpress new post interface. I even tried pasting it into Notes first (and it did paste into Notes) but that also failed as far as getting it to Wordpress. I had to go to my Macbook Pro and copy it from an email to myself, the paste into Wordpress.com.