Equirectangular Environment Maps can be a nice alternative to cubemaps as they are pretty easy to handle (1 texture vs. 6 cube faces). Another advantage of these maps is that you don't need DX11 for proper MipMaps, so you can easily walk down the MIP chain for some simple IBL setups.
Unfortunately the material requires some trigonometric functions which will add a bunch of instructions.
Using this setup you can easily multiply a specular/roughness map by the MIPLevel to control the reflection blurriness by surface roughness.
IBL Example GIF (800KB)