I did the entire organic chemistry, biology and physics sections and only part of the VR section. I think that they were slightly helpful, but maybe not fully indicative of where your actual weaknesses (aside from giant, glaring ones) and strengths are since only a few questions from each sub-topic are asked. Although they were only slightly helpful for me, I can see how they could be more helpful for others. If I had to do only one section it would definitely be the verbal since this is the best practice for this section outside of the AAMC FL's. But, pace yourself for the VR SA and use it more as an additional practice source rather than one giant exam.