Unfortunately, I don’t think Vulkan is going to be wildly exciting for day-to-day end-users. Eventually, we’ll be migrating to a Vulkan-native shader format, though the existing shaders will be supported indefinitely (as long as Nvidia keeps distributing their Cg Toolkit/Framework). Once we nail the new format down, I’ll be converting most of the existing shaders to it. There may be other benefits that end-users will be able to experience but it’s too early to really tell right now.
Currently, on the Intel front, only Broadwell works well. Haswell works in-game but the menu doesn’t show up. Ivy bridge is currently broken (though maister just put up a PR that may fix it for ivy bridge; we’ll have to do some testing). Sandy bridge and earlier is out of the question, according to Intel. For Nvidia, their binary driver (i.e., linux and windows) supports anything after Fermi, and Fermi might make it in the future. For AMD, their alpha-ish Vulkan driver is Windows-only and GCN 1.2+, IIRC; no word on linux support.
Note: our current Vulkan context is Wayland (i.e., linux) only but we’ll be extending that to more contexts in the future.