Please overhaul the UI, following the Apple HIG.

Very fast and minimal. Feels like an iPad browser, on a Mac.

Use standard Mac OS customizable toolbars (e.g. option-command drag support, small/big size, right click to customize etc.).
Get rid of the raised buttons and use standard safari/finder style buttons. Same goes for the tabs. They should match Safari.

See the Terra browser on the iPad for an example of a great non-apple browser UI.

The buttons are not evenly spaced. Please fix this.
Dont mix Helvetica and Lucida Grande in the interface. You should probably stick with using Apples system font, Lucida Grande. If you decide to use Helvetica, use it consistently, everywhere, and make the whole app feel like an iPad app. Reeder is an excellent example of this.

It could use a new icon.

Overall a great app under the hood, but the UI needs a lot of work. Looks promising.

Justin Lowery about Lightning Web Browser