Product review (4 stars): It serves its purpose very well.
I've been using the same lint trap kit on my 120v dryer for over 5 years without a single issue.  I do have a 4' washer/dryer closet and I close the doors (unventilated) during warmer months to keep the heat from getting out.  However, I only clean the trap kit about once a month and usually just add water when I see the level is getting low in between loads.  Sometimes I forget to add water, but the worst that's happened is that I found random pieces of lint stuck to my W/D closet walls!  No mold, no mildew, and I have bad allergies so I would have definitely "felt" the effect of any such problems long ago.

I recently removed the aluminum tubing for the first time since I bought it to do a deep cleaning.  I found very minor traces of lint that my handvac sucked up in a jiffy.  Unless you have a really large dryer and do massive loads of really damp clothes pretty regularly, I don't think the warnings are any reason to not try this.  This little gadget is a wonderful solution for apartment dwellers with limited options. My only gripe is that I wish the construction was a little more solid.  The lid clamps are tricky, and I've broken off little pieces of plastic with little effort.  However, until I find a new and improved model, I'll keep using this old one 'til it falls apart.