I've had numerous hard locks dealing with downloading Wii VC/WiiWare software off the Wii Mode Wii Shop, as well as hard locks coming out of Bit.Trip Runner 2. That's on top of the massive loading times to get ANYWHERE on the Wii U. Back when the Wii U first released, quite a few podcasts would mention firmware install times so long they actually thought their console had crashed, which led to the Power Offs that led to the hard drive corruption Oblivion mentioned. The console's OS is just spectacularly poorly written, so that big Wii U firmware update Iwata promised back in January can't come soon enough.
I've never had any problems except before i manually configured my Wii U to connect to my router. Initial install was 1 hour, fully downloaded and installed, which is pretty long for a 1gb update but how people are so impatient they turned it off baffles me. The OS was quite slow, and had quite a few freezings getting in an out of games. Once it took 2 and a half minutes from the time i clicked on the NSMBU icon, to the game actually loading. Once i connected it manually to my router, it sped up about 10x. The difference was night and day. I think the auto-detection of networks was a bit stuffed, and because of the Miiverse and everything else, the console is constantly doing things online, which would slow everything down. As soon as it was manually configured as per the instructions on the Nintendo website, absolutely perfect. And since then updates have made the already fast OS even faster, so it makes me wonder how its going to be improved.
And you've had problem with VC/WiiWare games on the Wii Channel? I only last week finally got around to redownloading all of my purchases (about 25 total) and testing them all individually, with no problems, freezes or crashes at all.