I received Alcantara as part of the P85 package. I also have the pano roof. With the pano roof it is probably not worth it now that it costs an extra $1,000, and you also get this dark plastic bar that goes across your ceiling that divides the opening and non-opening portions of the pano roof. Believe it or not, this bar is not covered in Alcantara but is bare plastic. You'd think Tesla could have covered this piece, especially for $1,000 upgrade price.
With that said, I prefer the look of the Alcantara over the fabric. One of my loaners had fabric and it looked cheap. Also, the A and B pillar pieces didn't seem to fit together as well as the Alcantara trim pieces, but that could be my imagination. Maybe the fabric just made the joints more noticeable.