I would have to disagree with that statement. While it is true that position:relative; is used to establish a containing block for AP children that is not the only thing it can be useful for.
Relative Positioning can be used for subtle shifts of an element. If you know what you are doing it can also be useful for making source ordered layouts where large shifts are made from one side of the page to the other.
Content first using relative positioning
It is something that newbies don't need to be jumping into right away though. A common mistake that everyone new to css makes is that they want to set position:relative; on every div when they don't fully understand how it works. There are times when it causes no problems at all but they need to understand when and where to use it rather than just using it blindly.
Absolute positioning should only be used for small chunks of a page where you intentionally want to remove the element from the page flow. If it has textual content in it then adjoining elements in the page flow should have a margin or padding buffer to preserve the AP element.
The advantage that floats have over AP blocks is that they naturally allow text to flow around them. They can be fine tuned into position with margins. As far as any IE float bugs, only IE6/7 are the ones that present any major problems these days and most all of the bugs have already been found and documented with workarounds provided.