Why not read the reviews on the Store?
I'll write about my experience here and may post it as a review on the Store at some point, whenever I feel comfortable that my review is thorough enough.
My devices: I own an iPhone 7 Plus, an Xbox One S, and a 2017 Surface Pro (SKU 1807), and for this review I'll focus on the iPhone and on the Xbox. All three of my devices are connected via 802.11ac wifi.
AirServer for Xbox One does have problems, but I'm still glad I bought it because so far, its problems aren't severe enough that they outweigh its usefulness. I like AirServer for Xbox One, despite it's flaws, and I expect it's developer to continue to improve it to fix it's flaws.
I'll start by talking about my experience AirPlaying video content from my iPhone to AirServer: not screen-mirroring, but AirPlaying video from my iPhone using the video's playback controls. (The AirPlay icon appears together with other playback controls when I watch a video on my iPhone).
First of all, you cannot AirPlay DRM-protected content, such as TV shows and movies on Netflix, Hulu, and other subscription streaming services, and you probably can't AirPlay DRM-protected video content that you've bought on services like iTunes and Vudu. You can, however, AirPlay DRM-protected audio content, such as Spotify, though it would make more sense to use Spotify's Connect feature to cast Spotify's audio from one device to another instead of AirPlaying it. AirPlay does have one advantage over Spotify Connect: the ability to AirPlay audio to multiple AirPlay receivers that are synchronized, though I haven't tested this.
I AirPlayed Apple's March 25th special event from Safari on my iPhone to AirServer on Xbox One by opening the video in Safari on my iPhone, starting playback, and AirPlaying the video using the AirPlay icon that appeared alongside the video's playback controls. I didn't use screen mirroring; I AirPlayed the video itself. It worked overall, but I noticed that if I paused the video and left it paused for more than a minute or so, the AirPlay stream cut off and the video would reappear on my iPhone as if I wasn't AirPlaying it. That was fine; I simply needed to AirPlay it again when I was ready to resume playback. I'm not sure that the same problem wouldn't occur if I were AirPlaying it to an actual Apple TV.
I've also tried AirPlaying video from within a news app called Haystack.tv, an app that I have on my iPhone. I am not talking about screen mirroring; I'm talking about AirPlaying the video itself, using the video's playback controls. I've noticed that AirPlay cuts off more frequently there. I haven't noticed it happening in the middle of a video, but I have noticed it happening sometimes when videos change (a video about one news event ends and a video about another news event begins).
About screen mirroring: it's been flawless for me. There is delay--perhaps one second--so if you are thinking about mirroring your iPhone's screen to AirServer Xbox One Edition, and playing a game on the iPhone while watching it on the TV, the latency will make many games unplayable (besides, some games may be hard to control if you're watching the TV instead of watching where you touch the phone's screen).
Summary: I'm glad that I bought AirServer for Xbox One, because despite it's flaws, it has worked good enough for me so far.