User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:27.0) Gecko/20100101 Firefox/27.0 (Beta/Release) Build ID: 20140212131424 Steps to reproduce: Upgraded from 26 to 27 in a Mac running OSX 10.8.5 Lion Actual results: The autocomplete menu is slow and flies off, it blocks me from typing until the animation is complete, which is annoying, defeating is productivity enhancing utility. I wish i could disable it, or have its behavior fixed. I made a screencast of the issue http://www.youtube.com/watch?v=OaExYIZWJ0I Expected results: Instantly show, right above the word i'm typing and quickly responde to tab being hit.

Works for me with firefox-27.0.en-US.linux64, 2014-03-02-03-02-03-mozilla-central-firefox-30.0a1.ru.linux-x86_64. Please try with a Nightly build http://nightly.mozilla.org/ (create a new profile https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles ).

Yup, in nightly the bug is fixed. Works as in FF 26.

Guillermo, thanks for the bug report and testing. This is a duplicate of bug 961431.