Clean and pleasant (should be called Troposphere or something as it reflects the beautiful silverwhite-blue skies here in the NW) and readable except for miniature icons - I find any design or ornamentation just compounds the complete absence of tab definition.
I feel like a Tab Hunter (that's a joke, kids.) This smooth neutral grey background does have the best chance of rendering most intentionally eye-catchingly colorful icons — except (ahem!) for Apple's logo, which practically vanishes on my screen. What's with their eschewing of color?
Do I have control of any of these aspects? I can't find any.
IDEALLY the sizing of icons and their spaces would be dynamically sized with additions and removals – as I assume your (invisible) tabs and the OS Dock are.
Keep up the good work