I think it's ridiculous that all downloaded content on my Wii can only be "transferred" to my Wii U rather than being "copied" (i.e. existing on both consoles at once). This leaves me in the precarious position of having to decide whether I'd rather keep my Wii with all the content on it or move it over to the Wii U, thus rendering my Wii empty and useless. Why can't we have our purchased digital content on both systems?
It seems easy enough to implement. Simply create an online infrastructure that keeps track of which Nintendo Network user has purchased which digital content, and allow that user to download that content on any systems he wants. That is the only acceptable structure, IMO. Anything short of that is a rip-off.
The menu load times are slow indeed, and I get network errors frequently.
Friend messaging should be integrated with games seamlessly.
As awesome as the pro controller is, it should have some sort of motion-sensing ability, which would allow it fully replace Wii remotes (a last-gen controller). It sucks you need several controllers to fully enjoy Nintendo Land (gamepad, wii remotes with motion plus, and nunchucks). You should be able to fully play any game with just a gamepad and pro controller(s).
I actually have not had a problem with the gamepad battery life. Since it came with a charging cradle, I simply cradle it when I'm not playing, and it's always fully charged when I need it. Even if it gets low, I can plug-and-play. I tend not to play continuously for over 3 hours...usually. When I was kid, things would've been different, lol.
That's my honest critique; now for a defense. Overall, I love the U. It has a lot of potential and already is worth buying for its unique experience. People say it has a weak library at launch, but what system in history didn't have a weak launch lineup? They all did. Actually, I had no trouble finding three games I wanted at launch: Mario U, ZombiU, and Tekken Tag 2. For me, that's enough to last months before I'll need another game. MiiVerse is awesome, as is the ability to control one's TV with the gamepad. Aesthetically, I love the black and blue styling. It reminds me of the PS2.