few applications handle poser shaders, actually I think the only one other than Poser is Vue, so you should keep that in mind. P2L makes some intelligent guesses on what Lux Shader matches the Poser Shader in question. there's some adjustments you'll need to make - all done in the exporter, nice and neatly.

as to the rendering speed, Lux can take sometime yes. but balance that with it's cost, the ability to use GPU Hybrid rendering, network rendering and being able to pause, save the render state, then reload it later and then coming back and restarting the render from where you left off, it balances out somewhat.