I will admit, in Pre-Release 5, some things have gotten a little heavy on the GPU. I wasn't able to run the program yet, because I haven't install NVIDIA drivers yet on my fresh Linux install.
Of course, things work mostly smooth now with NVIDIA drivers installed. But rendering time is much longer now and more heavy on my GPU with the lighting system being overhauled among other things as well like reflections being added.
Mine-Imator 2.0 is an insane overhaul and really is aiming in the right direction.