Nintendo, like many hardware manufacturers, was cagey about the final specs for the Wii U, choosing not to reveal the system's overall memory prior to release.
Now that the Wii U is out, though, it hasn't taken long for someone to tear one apart and do the detective work themselves.
The crew at PC Perspective raced home and opened a launch-day Wii U up on a livestream. While they didn't solve all the system's mysteries, like what its GPU is like, they did claim to ascertain how much system memory the Wii U is packing, and how fast that memory is.
360: 22.4 GB/s + eDRAM for framebuffer
PS3: 25.6 GB/s main memory BW + 22.4 GB/s graphics memory BW, no eDRAM
GTX 680: 192.2 GB/s :P
That's raw speed, mind you; the Xbox 360, for example, only has 512MB of DDR3 memory, but can do more courtesy of the system's eDRAM. What we don't know yet is how fast the Wii U's eDRAM is, and how much it's going to help matters when we do. Which is a pretty important thing not to know.
It's a little silly Nintendo can't release this kind of information themselves, as not doing so has left us with half-truths, which as you can probably predict can often confuse more than no-truths. I mean, it'd be easy to look at this and assume the Wii U is, in simple terms, a less powerful machine than its current-gen competitors.
But it's far from the whole story, and we won't get that until people have had time to really get under the console's skin and do some tests on the complete range of hardware.
You should also note that these findings come as a result of a fairly speedy third-party appraisal; you might do well to wait and compare the findings against those of others once the machine has been thoroughly torn down before considering them as gospel.
Nintendo Wii U Teardown [PC Perspective]