Unload inactive tabs' pages from memory, and session restore them if/when their tab is next selected. This could significantly reduce Firefox RAM consumption when many tabs are open, and also greatly speed up restarts (as tabs would only be loaded as needed rather than restoring all tabs immediately). Obviously care would have to be taken with things like Flash applications which might lose their state if reloaded.

Highlight tabs opened from the parent tab that belongs to some group, with different color.

For example: you open 3 links from tab A and get 3 tabs - lets call them B,C,D. All four tabs get coloured green, for example.
Then you go to tab C and open link from tab C and get tab C1.
So it would be nice to highlight tabs C and C1 differently - for example, color half of the tab green, half of the tab blue.

Use a proper tree, as in Tree Style Tabs, where any subtree can be dragged around, collapsed or closed. To fit groups into this model, surround groups with 'folders', so all groups are tree subtrees. These folders also provide a central place for all group operations. I suggest auto-naming the folders by listing their domains in order of first occurrence, though fussy users would be able to rename them. See mockup: http://tinyurl.com/tk-mockup-main

Your extension is great but update it to work with FF 3.7 and TMP.

The tab bar (especially when vertical) should have a find-as-you-type search box letting you filter the tab bar by title and url (and optionally page text) to help you find tabs faster. See mockup of the tab bar after filtering by "goog": http://tinyurl.com/tk-mockup-searchresults

If you autohide the vertical tab bar it moves the page when shown. It would be A LOT better if it instead could show over the page (overlay) and keep the page in the same position as it is.

it would be nice if you could show/hide the tree bar with a hotkey

Please update Tab Kit to work in Firefox 3.7a1pre nightly alpha builds, available from http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-trunk/ . Dragging tabs to change their position probably won't work: in fact, it will probably make Tab Kit freeze. That will be something that will need fixing.

For higher level tab organisation, let users have multiple independent trees of tabs, called workspaces, which they can switch between using a dropdown (there’s no need to show available workspaces permanently onscreen, as the user should have few enough that they can remember the important ones). These should be persistent across sessions and across windows until deleted (so no more session restore prompts). See mockup of dropdown: http://tinyurl.com/tk-mockup-workspaceselector
See also https://bugzilla.mozilla.org/show_bug.cgi?id=505214

Make highlights (unread tabs, current tab & protected tabs) prettier, for example unread tabs could simply be bold (as long as the current tab is kept distinct). Alternatively, add color pickers to people can customize this.

Hi,
TGM short explained grouping many Tabs in seperate Tabs (like a new seperate Firefox Window only in the same Firefox as a Tab).
Problem if normal Tabs are folded up by Tabkit and you change the group Tab by TGM and change back the normal Tabs are folded down.
There were a coop with TGM great.

Fade inactive tabs with age, like Dao's Aging Tabs (https://addons.mozilla.org/en-US/firefox/addon/3542), or else try and be compatible (if possible!)

Let user 'pin' tabs that should be always visible at top of tab bar. These wouldn't be affected by the scrollbar, but would be collapsible like other groups. See mockup after collapsing: http://tinyurl.com/tk-mockup-collapsedpinnedtabs These would be persistent across sessions, and workspace-independent (once those are implemented).

Highlight tabs whose titles have changed (for example GMail updates the inbox unread count upon receiving new mail) in the same way as unread tabs.

With certain themes like Chromifox and Chromifox extreme, the colours 'leak' from the tabs and make it look ugly.

I would like an option to disable the colouring of tab groups. (it would make it less organised, but it's a good compromise)