Regardless of whether or not most developers are upset about Safari's performance, most users would very strongly welcome a faster web browser. I'm pretty sure speed, stability, and ease of use are the main reasons Chrome is such a popular browser on the desktop. The thing is, it is not really that much faster than other browsers. However, even that small difference feels like a big difference and wins over many users. I'm sure many developers are aware of this. You can't get away from the fact that only allowing one browser rendering engine has some strong disadvantages and is one of if not the biggest disadvantage of using iOS.