I just installed a poret foam matten filter on the side of my 20 gallon tank. So far the tank is clear and I'm happy with it, but it's a very low bio load tank so it's not that stressful of a test (4 dojo loaches and a BN pleco). Anyhow, the real test is two years from now if I've never cleaned it and the tank is clean still
As of now I intend to install one on my future 300 gallon, but plans are made for changing....
For pros and cons, do you mean in tank matten filters / HMF, or do you mean using poret in a sump?
I am using Poret in my big Eheim 2260/62 filters and loving it. I'm using 10 PPI and 20 PPI cut to fit as well as the Eheim Ehfi Mech (coarse mechanical) and Substrat Pro or similar bio media.
The only con I can think of is the initial expense to purchase which I don't find that expensive in the long run.