I have to admit, I have only used Mario Kart on WFC, and it is a free network, but it is so unbelievably badly implemented I cannot fathom why they even bothered, its just awful:
- constant, frustrating waiting for the next race, to join a race, to find other people.etc
- constant and persistent disconnects even using a wired ethernet connection
- inability to communicate with either other players or nintendo
- overwhelming volume of cheaters who have hacked the Wii, and have infinite power-ups
- inability to select races intelligently: what if I despise the mirror cups, and don't want to play them, i.e., why can't I select by race instead of a group of people?
- obvious "partnering" where one player sits back in last to interfere with the other players while their "friend" retains 1st place
- control nowhere near as precise online as when playing offline, turning, etc., is very difficult online
I can go on and on, and will probably remember 10 more after I hit "submit", but these are a few major ones.
Nintendo did a terrible job implementing the WFC, and I would rather have a pay-service that is good then a free one that sucks.