Not really a review, just a question on the add on. Is it possible to move the vertical tabs to the opposite side of the screen?

Good add-on but you can't change the way the tabs look, apart from four (not too good) preset "themes". Moreover, the "themes" override the tab text colours, so "unread", "unloaded" or "read" tabs look the same.
You can set an option to "underline" unread or "strikethrough" unloaded, but nothing more.

Good but needs a CSS over-ride section in the settings, like the one in Tab Center Redux. I have a 14in screen and I'm not into the little fonts or the default themes. It would be nice to be able to override them via CSS mods in preference section.

I read that some users are having trouble getting rid of the tabs on top. They should know that it's possible to do via userChrome.css. Open your firefox profile folder, make a folder called chrome and make a new text file called userChrome.css in it. In that file add:

#tabbrowser-tabs {
visibility: collapse;
}

Is it possible to add 2nd function for the toolbar button - dropdown list of tabs? Sometimes it helps to have panel with all tabs on the side, but mostly I need just fast access to one tab, - so list with 4-6 words of tabnames besides favicons (which Firefox tabs can't give by design) would be more productive solution.
Yes, there is such addon already, but design is so awful, that I cant use it.

It good, just not what I want - it takes up too much screen space. If it could be made narrower to the point where only favicons were displayed....

On a side note - to hide the tab bar Firefox stuck up top, add the following to your (user profile)/.mozilla/firefox/chrome/userChrome.css file:

/* Hide the tab bar */
#tabbrowser-tabs { visibility: collapse !important; }


If you want to move the tab bar below the toolbar add:

/* Tab bar below Navigation & Bookmarks Toolbars
For best results, show Title Bar or Menu Bar */
#nav-bar { /* main toolbar */
-moz-box-ordinal-group: 1 !important;
border-top-width: 0 !important;
}
#PersonalToolbar { /* bookmarks toolbar */
-moz-box-ordinal-group: 2 !important;
}
#TabsToolbar { /* tab bar */
-moz-box-ordinal-group: 3 !important;

Looking forward to a version that's more compact (or ideally moves tabs to bottom of screen).