Too much drift and shopping, not enough racing.
Firstly, upgrading parts requires driving all over town to buy them. In NFSU-1, upgrades were instantly available after winning enough races. Also, half the parts available are what I consider "fluff" like hydraulics, stereo components, and headlight colors. I mean honestly, who cares? If I'm going to spend half my time driving around to buy stuff, I want it to enhance my ride.
Secondly, the downhill drift competitons are incredibly frustrating. I like a game that is challenging but winning the downhill drifts in the Heights are strongly depending on the luck of the draw if oncoming traffic happens to be in the right "zone" to get the most points. You'll find yourself replaying the same drifts over and over again just to squeak by with the passing score.
Thirdly, what the *#($)# is up with the nasty, skanky hoes on the mag covers. I wouldn't lean my bicycle against them. "Yo! Could you please get out of my shot, you're ruining it for the rest of us!"