I'm sure you're aware of this and I'm sure it will probably be worked on soon, but at this time, turn by turn doesn't exactly return the fastest results.
I tried doing a simple, three mile route from my house to a friend's house. The directions do start in correct location and end in the correct location, but everything in between is a bit funky. I'm starting to see a pattern that perhaps Waze tries to give you the route with the least amount of turns. I'm not sure about that, but I think it might be true. Every test-route I've tried (I'm doing this on the waze site, not in the iPhone or Android. I do have Waze on the iPhone, though) routes me to go on main roads, taking very little turns, when simply following smaller roads but taking a few turns would go directly to my destination much faster.
I'm not sure what algorithm Waze uses to route directions, I'm not sure if it's in-house and made by you guys, or in collaboration with another group, but if it could be looked at a bit and made a bit smarter, it would be a HUGE benefit. Turn by turn, along with community traffic, are the two most important things Waze has to provide, and while it's understandable that there are some kinks to work out because we're in very early releases, I just wanted to shoot you guys a heads up.