The answer to the two most important questions are as follows, the GTX 980 will cost you around $560 compared to the $500 for an R9 290X and the GTX 970 an attractive $330 compared to $380 for an R9 290.  Availability is hard to predict but the cards will be shipping soon and you can pre-order your choice of card by following the links on the last page of Ryan's review.  Among all the new features that have been added to this new GPU one of the most impressive is the power draw, as you can see in [H]ard|OCP's review this card pulls 100W less than the 290X at full load although it did run warmer than the 290X Double Dissipation card which [H] compared it to, something that may change with a 980 bearing a custom cooler.  Follow those links to see the benchmarking results of this card, both synthetic and in game.

"Today NVIDIA launches its newest Maxwell GPU. There will be two new GPUs, the GeForce GTX 980 and GeForce GTX 970. These next generation GPUs usher in new features and performance that move the gaming industry forward. We discuss new features, architecture, and evaluate the gameplay performance against the competition."

Here are some more Graphics Card articles from around the web:

Graphics Cards