Well I got the Patriot Supersonic 64GB today and have been testing it for the last hour or so. I am pretty happy with the results.
Wii U:
Zelda: 28.338 (100%)
Child: 32.546 (100%)
Pikmin: 22.778 (100%)
16GB:
Zelda: 26.189 (92.4%)
Child: 30.874 (94.9%)
Pikmin: 22.410 (98.4%)
Sequential Read: 26.14
Sequential Write: 20.01
Random Read 512KB: 26.19
Random Write 512KB: 1.358
Random Read 4KB: 5.956
Random Write 4KB: 0.010
Random Read 4KB (QD=32): 6.005
Random Write 4KB (QD=32): 0.011
64GB:
Zelda: 24.177 (85.3%)
Child: 28.832 (88.6%)
Pikmin: 20.201 (88.7%)
Sequential Read: 34.98 (133.8%)
Sequential Write: 29.71 (148.5%)
Random Read 512KB: 33.97 (129.7%)
Random Write 512KB: 1.591 (117.2%)
Random Read 4KB: 5.241 (88%)
Random Write 4KB: 0.072 (720%)
Random Read 4KB (QD=32): 5.241 (87.3%)
Random Write 4KB (QD=32): 0.081 (736.4%)
As you can tell from this, I did CrystalDiskMark on the 16GB flash drive I was using, and the new Patriot 64GB flash drive which was much faster in all areas except random read times. Fortunately loading in games is sequential usually
I tested with Zelda Windwaker HD, Child of Light, and Pikmin 3 on my Wii U Deluxe. Its important to note that the video output was set to 1080p HDMI. I did my testing previously using an older CRT TV which was stuck at 640x480p, so switching to 1080p caused load times to increase by an extra second or two. I started timing right after clicking on the game and hearing the audible ding, and stopped when it said "Press Start" on screen, so a large portion of the time is the slow basic intros that can be skipped.
The total load time dropped by nearly 4.161 seconds on the best timing, and only 2 second on the worst. While this isn't as important for loading the game the first time, I'm sure loading between areas in game has also decreased considerably, though that is harder to time and check. Which results in much more enjoyable game play without waiting for things to load when you switch from one area to another.
I am also happy that it seems load time has reached its absolute fastest possible. Wii U lacks USB 3.0, and the disk drive reads at only 22.8MB/s. The difference in flash drives was around 30% faster for the new drive, but load times only decreased by an additional 6% or 7% showing that the files are now loaded as fast as possible and limited by either the USB 2.0 port itself or the internal hardware.
Just thought I should share my results