The aforelinked review has the full coverage on the R9 270X Linux performance and compatibility with results compared to numerous AMD Radeon and NVIDIA GeForce graphics cards. However, for those craving some more data on this $200 USD graphics card, or to run your own performance comparisons, with the Phoronix Test Suite I have been uploading data to OpenBenchmarking.org.
Searching AMD Radeon R9 200 on OpenBenchmarking.org will give my original results plus a lot more, including results that other Phoronix readers have uploaded when comparing their own system(s) against my official results. One of these result files I recently uploaded was 1310207-SO-AMDRADEON08 to look at the resolution scaling impact for the Gigabyte Radeon R9 270X under Ubuntu Linux.
In the coming days I'll also have the open-source driver benchmarks for the Radeon R9 270X using the latest Linux kernel Radeon DRM in conjunction with the RadeonSI Gallium3D driver, albeit it's in a similar boat to the Radeon HD 7000 series hardware in terms of features and performance.