Service pack 3 not updating
(No word yet on whether SP2 is affected by this issue.) KB #3162589 alone makes this (or the latest) Cumulative Update worth it.
(Right now, the KB article has been taken down anyway.) ⚠ Originally, this Cumulative Update introduced a regression which could lead to queries that use NOLOCK / READ UNCOMMITTED to behave as if they were under READ COMMITTED (so they can block and be blocked).Recommendation: Use the latest CU above; these fixes are all included.⚠ SP1 Cumulative Update #1 includes 141 fixes, including all of the fixes from the RTM Cumulative Updates published up to and after SP1 was released (CU #6, CU #7, and CU #8 - see this post for confirmation if you don't want to cross-reference all those fixes manually).It also introduces the ability to update multiple statistics on the same table at the same time (see KB #3156157).Recommendation: Apply the latest Cumulative Update above.
One of the more important fixes is one that involves partial (and thus incorrect) results from a clustered columnstore index with a corrupted rowgroup (more gory details in this blog post and KB #3067257).