Firefox 4.0 mockup Screenshots and features

Month back, Mozilla had released Firefox 3.5 version and then there were some rumors about the 3.7 version too, but now the team is testing mockups of the 4.0 version, where they posted a few screenshots and features that are being planned for the newer expected version. Inspiration being taken from Google Chrome?(Any browser trying to have tabs on top would be considered taking inspiration from Chrome :p)

Here are a couple screenshots, where the tabs are on the top and bottom, one of which would be taken up in the later stages of development:

Tabs on top:

Tabs on bottom:

These screenshots were taken while testing in the Windows OS, and there is no testing done yet on Mac OS.
Here are a few positives and negatives, about those concepts of top and bottom tabs -
Positives

• Save Vertical Space
• Efficiency/Remove Visual Complexity – Right now the tabs have to be connected to something. So we are adding an extra visual element for them to connect to.
• Shorter Mouse Distance to Page Controls

Negatives

• Breaks Consistency/Familiarity – Moving things confuses existing users.
• Title is MIA – With the space removed from the titlebar you only get the truncated version in the tab.
• Longer Mouse Distance to Tabs – Takes longer to mouse to a tab.
• Lost Space – Sandwiched in between the application icon and the window widgets you lose some space.

One more good feature with Firefox 4.0 should be Combo Stop/Refresh/Go Button. This is located on the end of the location bar and here are its features:

• Turns green when you start typing.
• Blends with the location bar when at rest.
• Turns blue on hover.
• Turns red when a page is loading.

Check the Mozilla Wiki for the mockups and ideas!