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Makes fullscreen obsolete but could use a few tweaks Rated 5 out of 5 stars
It's actually quite significant how much extra screen space this gives you. I've been using it for a number of months now and I don't think I would go back now.
However, there are a few quirks. I can't drag a bookmarklet or a link to the bookmarks bar because the chrome does not reappear when I mouse over that area. Instead, Firefox thinks I'm trying to add the link to the tab bar to create a new tab. When I put focus in a password field, all the chrome shows up suddenly, and it's a little disorienting to see the page jump down. I'm not sure why it does that, maybe to make sure we can see the SSL lock icon in the address bar?
Last note, with the new Firefox 14.0.1 support for Mac OS X Lion fullscreen, the chrome does not disappear in fullscreen mode. If it could do that, I would be VERY happy.
All in all these are fairly rare issues though, so I am very pleased.