The Black Canyon is a great run with high quality rapids. Many people complain about the portaging, but I personally think it is worth it to be in such a deep canyon. Most of the rapids are actually IV and aren't all that hard if you are and advanced boater. In my experience most of the portages are no-brainers; it's eather a clean line or a death run. I only remember 3 drops where the decision to run or not is a difficult one to make. I usualy save this one for later in the year - like august when nothing else is going. 700 to 900 is a good flow; although, it is still good at really low flows like 400. Be advised though, the waterfall is un-runnable at flows much less than 600 or so. This involves rappelling or jumbing off. For the portage - stay high on the right and don't cross the river until you have to. The portage can be easy or extreamly hard if you screw it up. Plan on spending the night, it is worth the weight. The poison ivy is no joke and is something to consider, and the paddle out takes fooor-friggin-ever. Enjoy, it is one of my fovorit Colorado rivers.