I have got in at bills crk once, but from there to usual get in is narrow and flat for 2k. The river is generally a g2/3 similar in rapid size to a low picton, even in flood the collingwood doesn't get too hairy. Min level around 0.8 (4+ hour trip) and the higher it is the faster the water.
and it is also quite pretty with franklin-esque rainforest overhanging the river.