Product review (4 stars): Possibly worth the trouble
I have been looking for these vents for a while. I bought two, one for the bathroom exhaust and one for the clothes dryer exhaust.
Installation:
Basic tools and talent are needed for replacing an exsisting vent. Installing a new vent requires access to some more advanced tools and you will need some problem solving skills. We have beveled siding on our house, this required some cutting and chiseling to get the vent to fit the house fairly flat. You install the bottom part on the house first, useing the pipe from the old 4" vent (if you have an old vent). No 4" vent is supplied with the product. I used aluminum vent tape inside the vent to connect the pipe to the vent. On one of the installs I had to chisel a pocket in the siding for the mounting bracket of the top part (looks like a pot with a lid).

Pros:
Must be more energy efficient and bug resistant than the standard three flap vent.
Looks good when installed properly.

Cons:
Only the basic instructions. Most people could use some help installing this product.
Product quality control could be a little better.
No screws or vent pipe come with the vent.
No good way to lock the vent pipe into the vent, this is where I used the aluminum tape.

Bottom Line:
The vent is not everything it should be, but it beats the alternative.