Appearance wise while lying on the bed it is no thicker than a regular comforter. Possibly thinner and less fluffy. The first morning my son had it my daughter was in his room and said "hey, why does it feel like your blanket is full of rocks?" Some weighted blankets are filled with poly beads but for 11 pounds of weight that would be very very thick, so the river rock is less obtrusive. Also the rocks are naturally flame retardant and if years later the blanket is actually thrown away or something the rocks can just go in some gravel. Poly beads would melt in a fire and cause horrible burns and of course they never decompose or go away.
Washing is a whole other ball game. It's too heavy to run through a machine I think it could break or unbalance a machine. And if the weight didn't do it a ripped seam and spilling rocks into the machine would! It can be spot cleaned. Or I have considered spot cleaning and hosing off on a sunny day. My son has his between his sheet and regular comforter so I guess that protects it a bit too. We have only had it since December and I haven't tried to wash it. You could e-mail the company and ask about washing. Also getting a dark color shows less dirt.
Karina--weighted blankets are used to provide deep pressure to kids (or adults) during the night if they have sensory integration disorder which occurs either by itself or is part of the symptoms of autism and Aspergers. Theoretically the deep pressure is calming and can help the person be more aware of their body and have a better sense of proprioception during the day. My son is a teen ager and does NOT sleep in or for hours on end like his peers, I was hoping this blanket would help him sleep longer and I haven't seen that result. I think he does get a more restful and comforting sleep and he enjoys the weight. I don't know that it's improved his body awareness either! But hey he likes it and uses it. And when we have slept elsewhere with out it he misses it. So the weight is comforting. I have heard of people using weighted blankets just because they like them though.