Marred by long load times,constant online dropping, and rubber band AI.
The load times are rather long, some a minute or so. This is perfectly fine if all data is coming from the server, but it's about the same load time online and off. Though, once a track is loaded for racing in single player you can repeat it very quickly as much as you want. This might be why the difficulty is so hard or rubber bandy.
I love kart racing games, I don't mind losing at the last second when it's fair and square, but I've found it ridiculously hard to stay connected after doing anything in the game. I've been booted after looking at the menu for online racing. Coming out of creation, career, single player quick, split screen, and while doing the time trial to try to get to be a part of the 10% for the day.
The pure enjoyment of the online racing and if you have a friend or three to play at home with, this game is a total blast. I love the ability to adjust your kart's over all preferred play style. Allowing for better drift control over handling and vice versa. And the edit tools are well put together. You can literally make things in seconds and refine for hours.
I'm sure at some point the online connection issues will get ironed out, maybe it's a hardware fault on the server end. Not sure, as I'm not the system admin for the servers, but it can work well at times while others it's rather frequent dropping. I did get disconnected at the finish line on race 4 of 5 on an XP series race but was able to join another once back at the ModSpot.