If you are tall, finding a monopod that will work well with an SLR might be difficult. Mine only extends to about 5', but my main use is with Mamiya C twin-lens cameras, or my MPP Technical. Both of those are heavy to hand-hold for a long time. I have a Benbo ball head on mine so that I can lean into the monopod and keep the camera level. I got mine when I was doing a lot of hiking and cycling and carrying a tripod was difficult.
Used with care a monopod should give you an extra two stops slower shutter speed (subject and photographer permitting), but that is not my main reason for using one.