* Sound was choppy (driver-based issue), apparently this is again well-known: https://www.reddit.com/r/Dell/comments/5yvsng/xps_15_9560_au... there is no fix, the fix is to send it back (potentially also caused by Killer Wifi, Dell will never recognise that so you'll not get a WiFi card change)
* Mouse has a lag on the screen in 3D applications. Apparently, this is due to partially the XBox app that wants to record and isn't optimized to 4k + possibly McAfee + some other Dell boatware.
So, I returned the laptop. The 2nd thing in my life I ever returned. It was too much, and I wasn't sure I could fix all of the above in 2 weeks (return period in UK). I used Linux for my main OS, where everything but the space bar double-tap was a real issue. But that was painful. I was afraid that the replacement keyboard would be more or less the same. You can apparently just go to a random retailer, and it often double-taps there too (i.e. it will break). Worst about it is that Dell offered a BIOS update to "fix" this. The Dell Knowledge Base (KB) article detailing this has been pulled, BIOSes now come pre-updated (yes, I did update my BIOS, no, it did not fix it). When a BIOS update "fixes" such a basic hardware bug, you really ought to wonder about their quality control.
I can't believe that a machine as high-end as this has all those bugs. I've had an Asus $400 boondoggle from Best Buy for 4 years now and the worst thing it does is occasionally unmount the optical drive. It seems like Dell just has very poor quality control.
* space bar double-registers once in a while. There is a well-known issue with the space bar, extremely well-documented: https://www.reddit.com/r/Dell/comments/3ebe6t/dell_xps_13_20..., http://www.youtube.com/watch?v=R333HXzT7Ws http://en.community.dell.com/support-forums/laptop/f/3518/t/... and so on
* Killer Wifi BSOD'd 5 times in 1 week. Also well-documented, fix is apparently to complain and get an engineer to change it to Intel: https://www.reddit.com/r/Dell/comments/5r1fu5/xps15_9560_wif...
* Sound was choppy (driver-based issue), apparently this is again well-known: https://www.reddit.com/r/Dell/comments/5yvsng/xps_15_9560_au... there is no fix, the fix is to send it back (potentially also caused by Killer Wifi, Dell will never recognise that so you'll not get a WiFi card change)
* Mouse has a lag on the screen in 3D applications. Apparently, this is due to partially the XBox app that wants to record and isn't optimized to 4k + possibly McAfee + some other Dell boatware.
So, I returned the laptop. The 2nd thing in my life I ever returned. It was too much, and I wasn't sure I could fix all of the above in 2 weeks (return period in UK). I used Linux for my main OS, where everything but the space bar double-tap was a real issue. But that was painful. I was afraid that the replacement keyboard would be more or less the same. You can apparently just go to a random retailer, and it often double-taps there too (i.e. it will break). Worst about it is that Dell offered a BIOS update to "fix" this. The Dell Knowledge Base (KB) article detailing this has been pulled, BIOSes now come pre-updated (yes, I did update my BIOS, no, it did not fix it). When a BIOS update "fixes" such a basic hardware bug, you really ought to wonder about their quality control.