So far it is great I am typing up this comment using the S8+ in Dex.
It is great to use any of my Android apps in a desktop environment. I use more Android apps than Windows apps daily, so having access to those Android apps in a desktop like environment makes the whole experience so much greater.
But there are a few small things bugging me.
/* Audio: My mistake, this turns out not to have any problems... */
* Vibration: I am hearing the device vibrate when in Dex because it is not disabling haptic feedback.
* Fullscreen apps: Unfornately if your app doesn't support resizing it is only displayed in a fixed window size which can not be manually changed to anything other than a phone sized UI although you can switch between portrait & landscape, although this is not very effective when you are trying to use something like Microsoft Remote Desktop, video players or games.
* Singular notificaton pop-ups: This can often lead to notifications fighting over which is visible, and effectively makes it unviewable.
So my conclusion is that there are a few bugs, but surely they will be fixed with updates when Samsung is made aware of these bugs.
But I wouldn't write it off because of these bugs, as the device has only just become available to pre-order customers, so feedback is still required for Samsung to become aware of these bugs.
But well done to Samsung for making a usable desktop experience which imo is better than Remix OS by the way.
p.s. I'm not aware of how to report these bugs to Samsung directly.
Also worth noting is the fact that Android O supports launching any app (not just specially developed apps) on a secondary output display, I have tested this in a custom launcher I made for the Nexus 6P running Android O. This could mean that eventually we will be able to use Dex whilst the devices screen will still be usable for additional content.