I have an XPS 13 (2015) Developer's Edition.  The initial Ubuntu 14.04 install from Dell suffered all kinds of issues with the trackpad and with Wifi.  Dell recommended upgrading to Ubuntu 15.04 which I did.  The trackpad and wifi function much better under 15.04 however, I started getting random system freezes where everything hangs and the caps lock continuously blinks.    

After many weeks of trial and error, I finally found kernel 3.19.0-16 works well.  Today after an upgrade to kernel version 3.19.0.18, the freezes with Caps Lock blinking.  One final data point is that even with the 3.19.0-16 kernel, the system freezes with blinking caps lock when the command "sudo reboot" is issued.

Can anyone offer any insight as to the source of the issue here.

Thank you,

BP