Thanks Mom, I'm Sold!
Verdict: I absolutely love it. This paper greeted my gouache paint like a dear old friend. It wasn't too absorbent for washes, which went on nice and smooth. And I didn't mangle the surface while making the inevitable corrections and changes. Fantastic! Cartiera Magnani has been making paper in Tuscany since 1404, so by now they must know a thing or two. The only downside is that I couldn't find their paper at my local art supply store, so I had to buy it online. But that seems to be the new world order.
So, what about you? Have you tried the Cartiera Magnani Portofino? Do you have a favorite watercolor paper? Do tell all about it in the comments.