AMD's Radeon R7 260X is pretty much an overclocked HD 7790. It uses the same GPU with higher clock speeds on memory and GPU. A nice surprise is that the chip supports AMD TrueAudio, which makes it the only currently available GPU to support it at this time. Tahiti (R9 280X) and Pitcairn (R9 270X) do not support it. Another surprise is the use of fast 7 Gbps GDDR5 memory, but the R7 260X unfortunately only runs a 1600 MHz memory clock instead of the officially supported 1750 MHz. Gaming performance numbers are around 8% higher than those of the HD 7790, 17% lower than the HD 7850, and 24% behind the GTX 650 Ti Boost. These numbers mean that the R7 260X should only be able to handle full HD 1080p gaming at reasonable detail settings and without anti-aliasing, at least in most cases. Some of the more demanding titles will also require you to run lower details.
AMD's reference design cooler seems a little weak for the heat the R7 260X generates—the card runs a bit hot and the fan works extra hard to keep up. A card of this performance class should not be as noisy as the 2.5x faster GTX Titan! While AMD's cooler disappoints, I'm confident that board partners will soon release custom cards with better heatsinks that should alleviate this issue.
Back when I reviewed the HD 7790, it impressed with a very power-efficient design, but the R7 260X is not nearly as efficient, though it is based on the same GPU. I find this discrepancy in efficiency a little surprising and haven't found any definite explanation for it. Running at higher clocks might have a big effect on power, or performance may not scale as well with higher clocks on this chip (Bonaire), which would also affect the performance-per-watt metric. Its higher operating temperature also contributes to power draw, because the hotter a GPU runs, the more power it will consume to perform the same task.
With an MSRP of $140, the R7 260X feels quite expensive compared to other options in its price and performance segment. AMD's own HD 7790, while a few percent slower and lacking 1 GB of VRAM, retails at only $110. The 17% faster HD 7850 costs $135, and NVIDIA's GTX 650 Ti Boost, the current price/performance king, is 25% faster and only $10 more expensive. I could see AMD artificially setting a high price for their R7 260X to ensure existing HD 7790 inventory at retailers sells quickly instead of rotting on shelves for ages and would personally think $120 to be a more realistic price point for the R7 260X.