Useful for timing but that is about it. Some of the topics were similar, but I thought there was less crossover between NBMEs and Step 2 than Step 1.
I did NBME 3 and 4. They both underestimated my score, but 4 was much closer.
Edit: The general consensus on this board is that UWSA is the best estimator. Quite a few people claim it comes within a few points of your actual score. For me it came much closer than NBME 3 but not as close as 4.