If you have only played Super Mario Kart from the series, Mario Kart 8 has a radically different feel in terms of driving and physics compared to the oldest games. The most recent games are nowhere as slippery for instance, and handles drifting differently.
However, if you do enjoy the game, you can easily get several hundreds of hours out of the multiplayer and online alone (not to mention time trial mode of course

). The online has a pretty good netcode overall, besides some annoying quirks, but that depends on your connection and the connection of the people you're racing though. A really bad apple in the pack can alter and delay the item draw, but fortunately that's not too common. You're also guaranteed to find opponents for years to come, even Mario Kart DS and Mario Kart Wii are still played to this day despite no more official server support.
Item are quite determinant in this game, and there are occasions when there will be nothing you can do about your draw. Many people are questioning the item balance as well, particularly with how items are attributed depending on distance from 1st place rather than current rank, and the 1-item limit. Nonetheless, driving skill and item usage makes a noticeable difference in the long run, and the learning curve is fairly interesting if you're willing to put up with some of the techs. Not as significant as SMK, but enough to beat or even crush mediocre players most of the time.
Overall, you ought to at least try out the game before considering buying a console just for it. Being a SMK fan doesn't mean you'll like the game upon testing it. There are other good games on the Wii U at least, but still...