Even though the new Nexus 7 hasn't been officially announced yet (it should be today), it's already gotten fully benchmarked - thanks to Android Police - and we know it has a quad core 1.5 Ghz Snapdragon S4 Pro with Adreno 320 GPU and support for OpenGL ES 3.0 (thanks to Android 4.3), 2 GB of RAM, and 1920x1200 resolution display, which at 7" is 323 PPI, and well into "retina" territory.
The new Nexus 7, codenamed "Razor", uses the same processor as the Nexus 4, and I believe this was on purpose, because they wanted to re-use the chip for cost-cutting reasons (which is needed for a $230 tablet), and also because they can just use the exact same drivers as the Nexus 4, and instead of writing new ones for other chips, they can optimize the old one, which is exactly what they did.
The Nexus 4 scored about 18,000 points in AnTuTu, and the new Nexus 7 gets about 19,000-20,000, so it gets about a 10% improvement. The same seems to be true for the GPU, because when tested in 3Dmark for Android, it got 7,188 vs 6,300 for the Nexus 4, in the "extreme" 1080p test, in which it got about 30 FPS.
The old Nexus 7 could only get 1,877 in the Ice Storm Extreme test, so the new Nexus 7 should be almost 4x faster for games (3.8x to be exact), which is a huge improvement. Of course, you're now using a 1080p display, instead of a 720p one, which is roughly 2x the pixels that the GPU needs to push, so if games are optimized for 1080p, then you'll "only" get a 2x improvement in FPS, but that's still a very worthy improvement from last year.
The other specs include 2 GB of RAM, 16 GB of storage for the $229 version, and a 5MP rear camera. Let's not forget the device will also arrive with Android 4.3, which is supposed to make better use of the GPU for UI animations, and also improve touch sensitivity, so not only will the device be much faster because of its new processor, but the software will be faster, too, and you'll get a much better overall experience, too.
Google should be officially announcing the device today at its scheduled event, so we'll know all the details about both the new Nexus 7 and Android 4.3, then.