CSS is fine until you want to build something specific. The amount of hacks required for even the simplest thing is amazing.
Want that UL to have it's LIs in a grid? Use float. Float was supposed to make text wrap around images, but we use it for the side effect of making block elements behave like inline. It also messes up the height of the UL, since it doesn't really contain any text to be wrapped around. You can fix it most of the time, but it's a hassle, and prone to break.
Want a UL to be on one line and centered? There's a hack for that! And it's completely unintuitive black magic.
Even the simple things like lining up elements with a fixed margin between each other and to the containing element was a great hassle up until just recently when we could finally begin relying on CSS 3 features.
It's a big stupid mess with missing features and features misused.
The basic idea was OK, with the selectors and rules. The execution as was 10 years ago, and to a large degree still is, was horrible.