The poor performance (as well as perf/W for all but 2D graphics). Compare it to an NVIDIA chip of similar die size, TDP, and target form-factor. You'll realize that most Intel chips (other than the top of the line like the P580) are not in the same ballpark. As much as I hate saying this, NVIDIA's drivers are stable on Linux -- and I know because I use them every day both for display and compute (in OpenCL/CUDA).