LibreOffice Impress is horrifically bad. The Undo function is unreliable which is an enormous data-destroying pain in the ass when editing a presentation. The tools for editing text and vector graphics are also inconsistent and buggy.

LibreOffice is good enough for typing up a few simple paragraphs and occasionally tweaking the font.

Anything even slightly complicated, though, will look like a modern webpage rendered in IE6. This is merely annoying with Word documents, but downright catastrophic with PowerPoint slides. I don't care how many obscure features it can emulate if it can't even render line spacing properly.

Except for the Find feature that never works right. Cmd-F and try to paste into that box, for example. I use LibreOffice daily but that one is annoying. It crashes once a week too. I think LibreOffice is close, but I don't think most people are going to give up Excel for almost as good as Excel.