Update installed. Only played around with it a bit so far, but games definitely seem to load much quicker now. Booting up NSMB always used to put me just slightly in "Hang on, did it freeze on the loading screen?" territory. I'd say it's at least twice as fast now. Returning to the home menu is still sluggish, but even that seems a bit better. I'll be interested to see what the second update brings. I used to consider the Wii U OS borderline unusable due to the slowness. I'd still call it a bit sluggish, but if this was as good as it was gonna get I'd probably be fine with it.
Apparently this update also fixed the constant disc-spin issue, too. It also now can continuing downloading software updates even after powered off (added a new standby mode), and apparently the next update will bring full, 3DS-style spotpass (i.e., while you sleep, without prompting) update downloading. Nice.
Edit: Before/after load time comparisons from GoNintendo: http://www.gonintendo.com/?mode=viewstory&id=201237
Long story short, roughly 40-50% faster across the board, EXCEPT for System Settings. (Man, what is it with System Settings?)Edited by ThisOneKidMongo - 4/25/13 at 8:14pm