Like several other Rx 200 series graphics cards, the R9 280 is more or less an existing "Tahiti" graphics card re-brand and not a new Hawaii-based graphics core. The Radeon R9 280 comes in as a slightly faster version of the Radeon HD 7950 with a Boost frequency about 8MHz higher and this also means a slightly higher TDP. The rest of the Radeon R9 280 specs appear close to the same as the Radeon HD 7950.
Unfortunately we don't have any review samples of the Radeon R9 280, but there are plenty of Radeon HD 7950 benchmarks (only a portion are shown on that page) on Phoronix as I had bought that graphics card long ago. The Radeon R9 280 should work well with the AMD Catalyst Linux graphics driver and thanks to being another GPU re-brand should already work decent with the open-source RadeonSI Gallium3D driver stack. For best results, you'll want to be running the very latest code, ideally Linux 3.13~3.14 and Mesa 10.1~10.2-devel.