Well been playing this mostly since it has come out.
My thoughts:
Looks and runs great
Bit on the easy side
Multi player is good but ranking system is not quite right. Seems everyone can rank up to number 1. I would have like to see a proper system like we have seen for other games.
I was a bit disappointed to see the release of dlc unlocking everything even before the game was officially released. Multi player could have been stretched out if the good cars had to be earned.

Will I be playing this game for the length of time the BP had me? Very doubtful.

I totally agree! I like Split/Second but as you say its a tad too easy. Ive not yet tried the online modes and I'm a little annoyed that they released game unlock 'Keys' as soon as the game was released! At least Criterion waited nearly 2 years before releasing the Time-Savers Pack! Its utter stupidity if you buy a game and then open everything instantly! (in my honest opinion) Where's the challenge in that?...