Pretty sad to see that the reception has degraded in the X model. I understand if previous models had excellent call quality, that losing 1 bar on average is not a big deal, but it appears the quality of calls is also being effected to some, as their voice goes out occasionally, or faint as some have mentioned, with lower bars.
Considering this is Apple's current flagship phone, and that the phone didn't shrink in size (it got bigger), I can only see this as them cheaping out on overall quality design. Big mishap, and in my personal opinion, goes in the book of reasons to potentially stop buying apple products in the future, alongside throttling and a few others things.