Based on some comparisons with Mario Kart...
Pros:
-Lots of things to unlock, such as characters, courses & music tracks using the 'shopping' mode where you collect & earn 'miles' as tokens to purchase these things by racing etc
-Many other modes such as battles & missions, as well as time trial & all the other jazz you'd expect
-Online Play
-Unique All-Star moves for each character which make them more individual compared with Mario Kart
-The Sega wheel is an added bonus & makes the game kinda more realistic & fun
-If you love speed, this game is for you! Very fast paced feeling compared with Mario Kart which seems a bit too slow sometimes. The drifting makes this game also I feel
-Great graphics & themed courses
-Opa Opa is in the game!!! Very old school!
Cons:
-No ranking system for Online Play - (Personally my biggest let down!)
-All Star moves not available for Online Play (Spose it will be fairer too to stop people from trying to be last in order to get into first place with an All Star move!)
-Sometimes the frame-rate can be a little bit noticeable and laggy
-Quite slow loading times
-No map of the course during race which would have been quite useful, but I guess you would get used to the course after numerous amounts of playtime.