I own 2015 WRX and the OEM spoiler was getting bad rash with the clearcoat starting to crack and fleck off after 8 years So I upgraded to this and was definitely glad I did. It looks great and gives a nice contrast against my WR Blue color and looks massively better than the stock OEM black parts.
I opt'ed for using 3M Double-sided tape instead of the included adhesive as wasn't sure how it would impact the paint/clearcoat. You cannot use the factory OEM mount holes after removing the factory spoiler. Be prepared to clean that area thoroughly and have some way to seal the 5x OEM holes that will be left behind. I used high-strength electrical tape and it seems to hold up well to rain and car washes so far.
Make sure you properly align and do dry runs of attempting to see the duckbill on before going for the actual attempt. (IE: make sure you get the angle right so when placing it so rear of the trunk is flush with the duckbill)
Do not underestimate the strength of 3M tape otherwise you will risk cracking the spoiler, so set it on the car lightly first and making sure its flush all around before giving it some applied pressure to ensure adhesion.
I noticed after installation that a small area on my passenger side of duckbill rests JUST slightly high enough so its not making full contact with the 3M double-sided tape, or the tape is not 'thick' enough. It could just be my car, but food for thought when prepping install that you may need to double up.
tl;dr 10/10 product I love it and its fantastic upgrade visually, install isn't bad just be careful and methodical.