Product review (4 stars): It Works
Have to admit I was skeptical but this gizmo works as advertised. It's not very big and is easy to set up.  Of course there is nothing like an external vent, but this can suffice in its stead.  I found that my clothes dried as well and in the same amount of time as when my dryer was vented (my apartment building sealed up my dryer's external vent as the result of a refacing project).

Be warned, it does shoot off dryer heat and of course some humidity as the result of moisture initially leaving the drying clothes. Early in the drying cycle there is a mild odor of dampness, so it is best to keep the door to the dryer closet open to let it all escape.  I have no reason to believe that any lint got through the trapping screen.

In deliberating between this and a very expensive new washer/ventless dryer set up, this choice was a no-brainer, at least until either my wash machine or dryer gives out, hopefully never.