The wii online was awful, no excuses for that. It took months before it finally managed to connect to my wi-fi, which was good at the time. Then SSBB kept disconnecting in the middle of matches, was one of the reasons I gave up wii early because i couldnt stabley play games like ssb and mario kart with friends, but i could play cod + fifa on ps3, or street fighter.
Not sure how good it is on wii u as havent really had a reason to go online, except initially.

Much better than Wii online.

- The internet browser is very fast and incredibly handy thanks to the gamepad. It's basically a cheap Ipad, except you can't leave your home with it. 

- I never had to recalibrate my internet settings on the Wii U while I had to do that many times on the Wii. 

- I've experienced lag-free online with Mario Kart 8, Super Smash Bros. Wii U and Bayonetta 2.

- It's easy and fast to download games from the Eshop or Virtual Console. 

- There's some cool stuff on Miiverse. And some games have integrated Miiverse support that can be fun (Super Mario 3D World and Zelda: Wind Waker HD come to mind). 

My only gripe is the lack of communication options when you're playing games online.

Who seriously cares? I often see people use this argument, but these are all things that seem to have little to no use for me... 

It's a home console, I only play on my Wii U when I'm at home. 

How come steam can offer fully functional online for free?

I found that if you challenge a random person to a battle and both sides let it play out to the end (i.e. no one rage quits), either one of you can send a friend request afterward in the "Would you like to do anything else with _____?" screen. So go battle him, and then friend him. ~_~

No party chat. That's been on Xbox 360 since 2005 or 2006 (i don't remember if it was added a little after launch), PS3 hasn't got it neither but at least with the 8th generation Sony has fixed that issue, thing that Nintendo hasn't done.

And many Wii U games such as cod ghost don't even have voice chat, come on not even voice chat? That's a joke.

On top of d21lewis said, the lack of unified account system, archaic digital game recovery, poor online stores, and not all games are treated equally for competitive multiplayer.

^ Voice chat is up to the Game Developers. Ninja Gaiden has it, Monster Hunter has it... What is it that those games have in common? They're both third party but working on Nintendo servers. And they have voice chat in lobby and actual gameplay.

People... If you didn't know, there's this feature on "Friend list", where you can check the people you've played with and easily add them as friends and/or message them.

Nintendo's online works whenever I use it, and it's free... I see no problem.

You know, I've been meaning to make this thread for a long time, because I have the exact same question. The people primarily putting down Nintendo's network are people who don't even have Nintendo consoles, or who have a 3DS and not a Wii U.

Basically, you can sum up the zeitgeist like this:

-Nintendo's online sucks because it doesn't have achievements, cross-game chat, or cloud saves, even though it is completely free and plenty of people would take free online over a paywall online with those extra features.

-When most people talk about how Nintendo's network sucks, they're not talking about the actual ease of getting into an online game or the smoothness of the gameplay, they're talking about the missing features in the point above.

-People think Nintendo sucks because you can't legally bootleg your account on someone else's console and essentially pirate your games there. The truth is, most people aren't half as worried as their games being lost, stolen or broken as they are whoring out accounts across multiple consoles for free game access, a la Netflix.

That's not totally true. There's voice chat in Monster Hunter Tri Ultimate, and another game that I can't remember.

So basically, it's up the the developer, but it is possible.