Topic: What to do?

when I first bought the WiiU it would not connect to the network, on a router/modem that was working fine for all 10 of my other devices. So i had to hard program in all of the Internet settings like DHCP and IP address. Got a new router and it did it all automagically but I still did the DMZ fix. There are great walkthroughs on Nintendo's support site. DO all of that stuff, you can get it to work, Wireless stuff can be wacky sometimes. You can try the port forwarding too.

Actually, if you are connecting but taking forever to download, odds are the DMZ or port forwarding should fix it, the router is having issues letting the system connect to Nintendo's servers properly. It sounds like it is throttling the connection, forcing the ports and connections will make the router let the Wiiu do it's thing.

Already been suggested, but try forwarding some ports or sticking the WiiU in DMZ.
If you don't know what either of those things mean, google them.

Unless there's a fault with the onboard wi-fi within the WiiU, I'd definitely say there's some ports that need opening specifically for the WiiU.

Maybe you have 'Lemon Broadband' instead

Don't know if it's related, but I'm on Virgin Media and I couldn't get my Wii U to connect automatically to my home network at all (no problem with my laptop, my Kindle, my wife's Galaxy smartphone etc).

Found I had to configure all the IP addresses etc manually in the Wii U's network settings (found a guide via Google). Have you tried that at all?

Had this problem with my DSi, Nintendo wanted me to plug in my laptop to my router and mess around with it through that, never materialized. Got a new router a few months later, literally never had internet trouble again.

As others suggested, try manually setting up the Wii U to connect to your router. I would agree to the group here that this is a router issue above all just by the way it sounds.

Also another one of those "do these things before you do other things" , have you updated your routers firmware any time recently? Might help

I've been having issues with WiFi as well, moved it, turned it, moved the routers, messed with the routers antennas. I still have connection issues half the time with eShop and internet. And I recall DSi issues as well. And the 3DS is annoying to connect when in a hotel. I bought an adapter for my Wii but gave it away to my sister or parents who couldn't get their Wii to connect at all over WiFi. Nintendo is just very bad at making WiFi work well on any of their systems.

Sorry I don't have any advice, just adding to the litany of WiFi issues.