Yup. Got it. Here are my thoughts so far:

1 - Single Player - seems fun, good tracks, AI surprisingly aggressive, lots of options for strategy and handling seems fine. No complaints and overall I'm very happy with the campaign so far (although I've been skipping the cutscenes)

2 - Basic character/kart modding - really good. Many options, particularly for your appearance, and crazy easy editor for the task. You could blow hours just creating your look and some probably have.

3 - track editor - really good, too. Easy to create a quick track and the auto-populate seems much better than the Beta. Getting more hands on is easy, too, and the options are very deep but very easy to use. A real big selling point for the title for me over other Kart racers. I can't imagine why anyone wouldn't want to make their own track with tools this simple to use

4 - split screen - very good. 2 to 4 players. Experience is smooth. Great fun for friends.

5 - online - haven't tried yet. Was a lot of fun in the Beta so expecting it to be good.

6 - sharing - really simple. Grabbing new tracks, cars, etc. is quick and easy.

The only downside is the load times. They're no nearly as bad as some suggest, but they are longer than you'd expect. The download of shared stuff is so fast though that I suspect it's bound up with the design of the engine, with tracks clearly existing as quick to upload/download information files that take longer for the game engine to then read and create for actual playing (that's my guess anyway, if the engine just had to support playing I'd bet the loading would be much quicker).

Personally I'd say it's a 90% plus title if you want a fun racing experience and accept that the creation side is not an extra but a core part of the title, just as it was for LBP.