These two tools is not that user friendly, and the learning curve might be steep. HOWEVER, once you got your hands on their tricks and trades... you can do wonders and finish up writing without the hassle of formatting like other Word processors.
For those who worry about OS compatibility, don't. Because these software are runnable on Mac, Windows and Linux. Not sure about BSD, but BSD fans could give them a try.
There is another thing I forgot to mention... these two software are available free of charge!