Had the S10 for the first weekend after official release here in Europe.
In summary, I think that the S10 is (for me!) the most refined version of an Android smartphone, which would have had the highest chance to push me to a switch. The new one launcher is usable (except for these ugly icons), overall the phone had a very "speedy" appearance, the display is stunning and the overall build quality is great. I liked the idea of the wide-angle camera and, even so it's a bit nerdy, I really like the concept of DeX.
However, the overall picture quality of the camera is (again in my opinion!) inferior to the XS. Especially in low light the pictures were sometimes unusable and the latter is already something where the XS is also not always impressive. The camera performance is quit important for me.
Anyway, there a two reasons why I would not switch: First, the overall Android experience is still not as smooth as iOS. It's a bit difficult to describe, because objectively speaking I did not had any stutters or related problems, however, for instance scrolling in a browser: While having in Safari some kind of real sense of the "kinetic energy", i.e., every move with your thumb results in an expected movement (speed and distance) of the webpage, in Chrome on Android it is some kind of speedy mess. Every touch results in some kind of hyper scrolling - it is difficult to describe. Nonetheless, this missing refinement concerns several areas on Android. This could be complemented by the note that apps are usually less well adapted. However, I would neglect that, because Android has apps that are not possible on iOS and therefore I see a break-even result (e.g., Adhell via Knox, Filemanagement, etc.). Second, the integration of iOS and macOS. The latter is not a fault of Android, just something that I appreciate about iOS. Continuity, Handoff, etc. - great features.
In sum, the S10 is great device and in some areas outperforms the iPhone. It would even be my "to-go" device fo Android smartphones. Nonetheless, the degree in which iOS is polished and the integration of macOS lets me stick to my iPhone.
Just my two cents.