I have been to a [10] myself, and this is pretty accurate.

Your perception of the world almost completely dissolves. No co-ordinated task is possible any more; even speech is difficult. You will quite possibly start hallucinating. I was at least in a state where I could no longer tell the difference between my waking dreams and the room around me. In fact, I'm not even sure I was aware of the room I was in at all, so completely had I receded into my own head. Your sensory input is amplified so strongly that it's impossible to make sense of anything. The smallest detail of colour, texture or sound that you notice completely overwhelms your perception, until you notice something else a second later and are completely transfixed by that in turn. Your sense of time also goes out of the window; the time I spent in this state felt like a good 2 hours, but the clock measured it as only 15 minutes around the peak of my high.

It's not entirely pleasant. A [9] is great; you still have minimal control over yourself and some awareness of your experience. A [10] is like being black-out drunk; you're not really aware of what's going on and you can't do anything. At least on weed you're not going to choke on your own vomit.