After tinkering for an hour or so, I realise, the Apps all individually look great, the minimalism and white space, keyboards and transparency effects work really well, but the home screen looks a bloody mess.
I know this is just one persons opinion, and this is Beta software that will see considerable tweaks over the next few months, but my immediate thoughts are that the "app grid" doesn't gel well with the new design aspiration - the grid is too dense, and it's predicated on all the icons being of the same style, so if you have 3rd party apps on the home screen, it'll look disjointed no matter how Ive and Co. try to make the icons unified. ironically, the most comfortable spacing and effect is when you're inside a folder, the title has some nice text and it's limited to 3 icons wide, there should be a setting to select how many icons you want per row!
And speaking of unification, all the gradients for icons go different ways, and the green icons or messaging are a bit too vivid and electric, which forces you to choose your wallpaper wisely, to either compliment the vivid colours, or contrast it.
The translucency of the "home bar" and folders is also too low, so they look much like just blocks of colour, and somewhat undermine what cute feature.
But this are minor gripes about the home screen, and it's difficulty in representing a pile of icons with consistency. by contrast the restraint of the lock screen looks great.
One thing I love is that for instance in a iMessage thread, each individual message has it's own physics, so where we normally have one plane that rubber bands when it hits the bottom, now each element jiggles a bit. Further to that, the plain colours in the messages are actually soft gradients from the top to the bottom of the screen.
hmm, this was a rambling post, but none-the-less i'm excited to see how they refine the OS, but it does sure need it ...