Yes, the Wii U's online is decent and definitely a step in the right direction. The Miiverse is a great addition and really brings out the friendly "Nintendo" community across the Wii U's library through its integration.
That being said, the Wii's online was atrocious and cumbersome to even get working properly, at least in regards to Super Smash Bros Brawl. It may be Nintendo's insistance on having both the Wii and the Wii U be incapable of connecting via a proper ethernet cable (as this was/is also the case with the DS and the 3DS, currently) but the shift toward and friendly, semi-connected online system works in Nintendo's favor.
It seems to work well (generally speaking) most of the time, but yeah, Brawl's online was awful, plain and simple.
[sub]Personally speaking, anyway.[/sub]