I have made several documents using LyX (running on Ubuntu 13.10). Some of them are five pages paper and a few full 20 pages report. I felt more grip to the interface, menus and some recommended tweaks. However on several cases I bumped into "line exceed margin" problem. There were one or two lines that overrun the existing page margin. I have googled it, but nothing came up. Until a discussion on Latex Exchange (maybe, I forgot) suggested to add "\sloppy" code in the beginning of the document.
I typed it then click the "re-run" button on the upper left, then all the overrun lines were vanished. I think LyX is forcing the hyphenation on the lines.
And finally my docs look neat, magically. :-)