Product review (4 stars): Superior to metal ducting, in some ways
Infinitely easier to work with than metal flex-duct.  However, as others have said, THE SMELL.  It's noxious!  After venting the... vent, outside for a few hours with warm-hot air, the smell dissipated, but is not yet gone.  I suspect the lingering odor will be permanent without some sort of chemical wash.  In the end, the odor is around 10-20% the original strength (like someone painting their nails in an adjacent room).  Beyond respiratory concerns, the ducting is mildly flammable.  I suspected the odor emission to be linked to flammability, so I cut a small length of duct and mated it to flame.  The ignition took and sustained for a few seconds before flickering out.  This is something you may want to consider if you have high-heat sources nearby.  Without total combustion, I suspect the duct would simply melt, eating up the vinyl and emitting those disorienting aromas I mentioned.  Please consider the environment in which you plan to use this ducting.  Hazards aside, this stuff is a joy to work with.  The vinyl is quite strong and covers both sides of the steel coil, so it shouldn't ever rust, and is far more flexible than steel flex-duct.  4/5