Firstly, I just learned about the core.pager option which solves the problems I was solving previously with this ugliness:
ll = "!git --no-pager log --pretty=nice -n30; echo"
Secondly, the %+d. I generally don't use the --graph log formats, (such as these), that show you the branch paths, but seeing where the refs are is super useful. The + makes it appear on the next line without adding a line break when there are no refs.
Here's a screenshot of how it looks (with details obscured to protect the innocent).
Update: I dropped the line break before the refs list, which is fine if you have a nice wide terminal, and tweaked some colours. Now it's:
nice = format:%Cblue%h %C(cyan)%cr %Cgreen%an%Creset %s%C(yellow)%d %Creset
