I slipped a few times but always recovered and there was never any real danger. I was lagging way behind since every step was hurting my knees. I found a big stick to walk with which helped a little, and we pressed on. Finally I came around a bend and saw that stream crossing, and knew it was over. We made it to the summit in about 4.5 hours, and the round trip was exactly 8 hours 5 minutes.
Weather can change quickly and it definitely gets colder up high.
Also rain gear even if the sky is clear.