Adding "clear: left;" to the h1's style seems to yield the expected result, perhaps the problem isn't with the floated items but instead with the blocks? Is there some new rule about the default clear behavior?
interesting - that first one looks like it might be a bug. When you inspect it in the debugger, the h1 is entirely within the container, though the text is well outside.
- Floats don’t push block content down (http://jsfiddle.net/cvalleskey/WD9pB/)
- Z-index breaking when element is a child of a fixed parent (http://jsfiddle.net/cvalleskey/9S3S8/)