I know that one of the big upgrades of the TinyMCE editor in 3.9+ is that the "Paste From Word" functionality is supposed to be included in the editor. However, I have not found this to be true. If you paste from Word or elsewhere where there's styling, it doesn't strip stuff out. I've found that selecting everything and hitting the erase format icon helps. But why remove the "Paste From Word" icon if the integrated version doesn't work? It was a lot easier to explain to clients when the "Paste From Word" icon existed and worked. Hoping that there will be a fix for the integrated version soon.