on IOS waze is incredible. It does voice notifications for traffic and has the ability to input accidents and such. I tried inrix but its horrible. The map view is bad and there's always a delay
Nokia Drive is the best out on WP8, it lacks a few of the features from the WP7 version but i Really wish that Waze would make a port. Been a fan of Waze for 3 years, nothing compares.
To answer the original question about pure traffic, I do like Mango Traffic as it gives you a general sense of where traffic is but certainly not as detailed as Waze.
I've stuck to Nokia/HERE Drive for the most part since coming over from iOS in November. Waze was cool on the iPhone but for some reason I actually preferred the spartan, utilitarian style of INRIX (I think INRIX may actually have better underlying data sources too). There's not much to it but somehow INRIX is still not as good on WP8.