Just putting this out there in case anyone is interested:
I removed the ASF from my XZU recently, as I found it annoying. The feel isn't as nice as glass, and ironically it's easily scratched.
However, the downside I found to removing the ASF is that the phone has no oleophobic coating underneath, making it a nightmare to keep looking even half-way clean.
There is a company called "Fusso" that makes a replacement oleophobic coating, but it's pretty costly. So when looking around for cheaper alternatives I found quite a few people have recommended Rain-x for this purpose. So I tried it out, and have been using it for a week and a half now. It certainly makes a BIG difference. My XZU is now just as smudge-resistant as my N10.
I'm not yet quite certain how long the coating lasts once applied. I first applied it over a week ago, and then re-applied a few days later. It's been a week since I last applied and the coating its definitely still effective. So in summary, I would definitely recommend this solution! The rain-x cost me just under £5, where the fusso coating is £20. The bottle will last for years.