Product review (4 stars): Works well but you need to know a few things.
After reading some of the reviews I figured I would take the time to say a few things....

First off... The reason dryer moisture is vented outside the house is because the designers knew too much moisture in the house can cause mold and health issues.  That being said I can only recommend this product as winter use only when the humidity is low to start with.

Here is a few thoughts.

1.  As others has mentioned this is not really a filter per say.  It's simply a small bucket that has water on the bottom of the unit.  You add in the water yourself.  The thoughts are that the lint will hit the water and get suspended and out will come semi clean hot air from the drier.  I would caution that the moisture from the clothes will be dispelled into the room in a good amount.  You can solve this issue by turning on your furnace fan to recirculate the air around the house if you have a vent in your laundry room.  Or... Just get a small clip on fan and push the moist air out of the room.  I use the furnace fan option and have no issues.

2. It will not catch all the lint.  You will have to dust a bit more in that room.

My purpose for this small unit is to add moisture in the house in the winter as it gets really dry down where I live.  Additionally if you stop to think about it.  All the air you are blowing outside the house is also leaking into the house in the same amount. Go outside and feel how hard the air comes out of the vent.  That same amount of air has to be pulled into the house so you are actually sucking out the heat you paid to make in the colder months and raising your bills.  In winter we have a heat pump that struggles in the winter to heat the house.  I decided to plug the outside hole from Nov to Feb and use that heat from the dryer I paid for to help warm the house instead of waste it outside.

You have to find the balance with this product.  We noticed some laundry soaps when vented in the house caused us to get head aches.  Obviously you need to be aware of this.  We bought a more natural soap and the issue went away.  You figure it cant be too bad because you are putting the clothes on your body but you really need to be aware of what you are doing.

All in all after a bit of trial and error we have a nice balance of adding moisture to the house as well as stopping heat loss.  Plus its nice to know the house is getting the benefit of the dryer heating the house in winter a bit.

One might ask.  Am I that cheap I am worried about dryer vent heat?  Overall no.  What I have done over the ten years I have lived in this house is look around at things I can do better.  As an example.. Install a clothes line in your basement and hang jeans and things you really don't need to dry.  Turn down the hot water heater to the lowest setting that you can tolerate showering. No reason to store extra heat your not using. Radiant barrier in the attic. Deflects heat back into the roof not your attic. Solar powered attic fan. Works like a charm and the sun powers it. House is all LED light bulbs.  Amazing difference in the power bill if you change them all. ( Save your old bulbs you take out and take them with when you move. LED bulbs last 10 years or more supposedly ) Install on off electric eyes on out door lights. Now we don't have to forget to turn off security lights in the daytime.  All these things together have chopped over $30 to $40 off my bill and I always have the lowest electric bill of my neighbors. That's over $400.00 bucks a year I can spend on buying other things on amazon. :)

Anyhow you will have to be the judge on this product.  The price is fine.  It is a bit hard to snap the two parts of the bucket together at first but I think as time goes on it will be easier.

Good luck.