I do not know if there are any limits to what or how much you can copy. I am going to download the toolbar today and play with it a little. I will pass along what I find through my fiddling around. I gather that it only adds data to a family tree that you host on Ancestry.com. I do not think it will import the data to your Family Tree Maker software.
If anyone out there gives the toolbar a try, let me know what you think. If you do not have it yet, you can click any of the highlighted links in the posting to download it now.