I haven't used Looks to any great extent. Coming from a decent comfort zone in Apple Color, Speedgrade is incredibly foreign. I like the concept that Adobe is going for to "redefine" color correction/grading, with the adjustment layers system. However, the actual program is confusing and non-intuititve. I spent a couple days trying to learn how to accomplish a basic correction, but had little to no luck. There isn't even a file menu within the program... Again, I think the idea is right, but the execution just isn't there (yet).
Coming from Color (the program), everything has a set area, with rooms for primary corrections, secondaries, effects, and so on. The timeline is consistent with the layout of the NLE programs, so everything is where it should logically be. I still don't fully understand how to navigate the Speedgrade timeline. Additionally, Color has all scopes available, whereas Speedgrade only has a parade waveform and histogram? Unless I'm missing a huge piece of how to fully operate Speedgrade, I will likely never open the program again until they seriously upgrade it.
These are just a couple of my initial thoughts that were strong enough for me to force a new workflow with Premiere Pro and Color..
* Also to be noted - when I was testing Speedgrade, I was in a trial of Production Premium - maybe the program was limited under the trial?
(Apologies for the negative rant and somewhat off-topic post)