I think it looks pretty good, but any major weaknesses won't come out until you strain with the weight a bit more.
A couple things:
Your toes seem to be pointing almost straight a head. They should be at least 45 degrees to enable your hips to get closer to the bar.
Your hips are slightly too high and too far away from the bar. In that dave tate video, he talks about dropping your ballsack on the barbell. When you lower to grab a sumo deadlift, your hips should be dropping as close to straight down as possible. Your angles look like conventional pulling angles, but they shouldn't.
This is a good example of sitting down to begin a sumo pull:
A plie squat comes from ballet and isn't exactly the same as what you want to do here, but the back angle and the direction of descent is.