I AM NOT the expert here and have not owned one. Want to make that clear up front, but I am farily familiair with the unit as I was going to do the same thing (and may still, but that is a long story). I have heard mixed results. I talked to one guy on his Valiant and he and his wife LOVE it. Cannot remember who he was, but he cruised the islands and I think he is in Guatemala right now... so if that person is reading this, chime up (I spoke to you outside Steve's office about six months ago). They used theirs for 2 years, no problems.
Now, that is about the end of the good stories I have heard. Many people hate them. TOm Neale stuffed paper towels in his. I am suprised that your marina does not have W/D facilities. Almost all of the ones I have been to that are Liveaboard down south have them. Also, I do not know where you are cruising, but down south you really don't go through a lot of clothes... not like living in a house.
I would like to have one too, as there are four of us (two kids).
I too would be interested in hearing both sides of the story. The units are not expensive in $$, but they are in space and water. Tough decision.