I just finished watching the first two episodes. The storyline has a much darker tone than Initial D, and the characters are more mature. Character designs are somewhat on the ugly side, but less annoying than those of Initial D. As far as the animation goes, it's exactly like Initial D: 4th Stage (and it's not just because they're animated by the same company), with its extensive use of cel-shaded CG for the cars. The S30 Devil Z looks stunning.
On the downside, Wangan Midnight's music is hard to define. Initial D stuck with Eurobeat, and it's worked over the years. Those who played the Wangan Midnight: Maximum Tune arcade game series will be disappointed by the fact that the anime does not use rave music. Instead, it uses generic-sounding J-Pop and J-Rock BGM with some Eurobeat leftovers. Other than that, the opening theme by TRF is very catchy.
Is Wangan Midnight better than Initial D? You can't really compare both, as they both have completely different styles of street racing. They're both worth watching, but if you're tired of seeing that white AE86 Trueno a billion times, try a blue S30 for a change.