It's a shame XPS never really caught on. I've had two situations where I've needed it. The first, we were setting up a Dispatch centre about 8 hours away from home. All we had were our laptops and tools and we needed to print out labels in Visio. Problem is, they wouldn't let our computers onto the network and nobody there had Visio. We decided to print out the files to PDF and put them on a USB drive so someone could print them for us. Then we realised some Print-To-PDF programs actually shrink the image by about 5% so all our labels came out too small (we need them to fit 100%). I decided to try an XPS file because I knew we had just installed a hoard of Clients with Win7. Printed from XPS and everything fitted 100%.
Anyway, to cut a long story short. XPS can be useful in rare cases, especially if you need things printed 1:1 with the dimensions all 100% identical to the original.