I love Zotero. It is my reference manager of choice. I have Endnote X, but no longer use it.
I just updated to Zotero 1.0.7 and received an error message when trying to import a citation from Google Scholar. I had not received such an error since the early beta releases of Zotero (I think 0.5). Luckily, I came up with a solution.
On the Google Scholar homepage, click on Preferences. Scroll to the bottom and tick Export to Endnote format, then click save. The error was then gone, and Zotero worked beautifully.
Zotero is a free download and is an addon for Mozilla Firefox and Flock.