There are still pple out there who utilises ultrabook laptops/small x86 UMPCs as their source actually, personally I've seen this under some japanese audio mag coverages for those that I buy and although this isn't exactly considered a common sight but still a niche, I do own some pretty sleek and lightweight UMPCs such as the Sony Vaio P/Willcom Sharp D4 paired up with USB DACs as my transportable driving sources actually.
Does the job well enough just that maybe in terms of outdoor battery life wise, cannot be compared much to nowadays the latest Android/iPad tablets or Haswell-based Ultrabooks, but at least in terms of overall weight wise my Vaio P/Sharp D4 when paired with my Fostex HP-A3 DAC/amp, is still much lighter than carrying a MS Surface Pro alone.