The player tools that bothered me the most have actually been nerfed: smites, stunning strike, counterspell. Not all abilities that bother me have seen changes, but enough to make running combat more fun for me.
The biggest improvement IMO is the new encounter building math and the powered up and streamlined monsters. Nothing was worse than struggling running a monster with 25 spells at the table, and then having a pushover encounter anyway. The new stuff is far better balanced, though not perfect. Just this has saved me so much time and worry that I find the revision worth it. Even 150 bucks.