I just wanted to add, live traffic info is marked on the map itself as others have noted, and you can also bring it up as a list on the left side of the screen, if you want to read it. It's sorted by proximity to your current location.
As for the confusion with arrows and color coding, i the arrows are for the 2008 i-drives only showing direction of traffic, it appears the 2009+ can show color or arrows?.
And yes, it works really well, sometimes there are 5 to 15 min delays to post new accidents, but it's a function of the city's reporting system to the data center, here's BMW's disclaimer relating to that:
it looks like this: