I love SlimStat - using this since it's beginning (5,000 downloads - easier to say than when it time it was). I'm a designer & developer, and realize what issues arrised sinse 3.8 WP release, especially in terms of design. I understand you tried to keep up with the new style. But please, change that, improve that, whatever, but make it look as good as before, I beg you :)
What I mean:
- the colours, thay should match the color scheme selected by the user. now it looks flat, but it is out of everything we have in WordPress UI
- text size is too large at large screens (RDW, I see, but not that way please)
- all the icons looked ok if when they were small (before the update), now it is not so good
- the panels, in my opinion, should behave more like dashboard widgets (as it was before), not to expand on large screens, but to have a predifined max width, so we can arrange it the way we used to before
- a scroller for data panels, I found it after couple of hours, it was so difficult to notice
My general impression - it's a huge step backward. But I really hope you'll push that forward again.