First of all - great job on shipping! This looks great for a first version, and I think it has good potential.
Granted I've only been using it for about 10 minutes, here is some feedback I have so far. I am using a fairly new Macbook Pro.
* panning between tabs is quite jittery and I get lots of jank when scrolling in general (vertical-in-tab or horizontal-between-tabs). Optimizing this might have been low on the list but I think it would make a huge difference in experience if it were smooth and snappy. I have a decent machine so I don't think it is a hardware constraint.
* The interface is a bit bulky, and layout can be improved, and I feel there is some wasted real estate. It may be a challenge to have visual cues for separation, but simplifying and cleaning up a bit would go a long way.
* When I focus on a text box or otherwise click on a tab, you should bring it into view. I understand there is a good use case for typing something while viewing another tab - but not if I cant see anything at all.
* Probably just an issue for folks with a Mac gesture pad, but the swiping to pan from tab-to-tab also triggers the back action for a page. Probably need to override the browser action and continue panning since that's the action I started with.
Thats all for now! Thanks.