Can I see my CPU and memory usage meters in the menu bar?
I use MenuMeters for this functionality, and have a hard time living without it.  How do other people know when their web browser is finally done downloading a page, or YouTube stalled out, or iPhoto still working, or ...?

MenuMeters is freeware, but well worth the donation.

The original author has stopped maintaining MenuMeters, but someone new has taken over for El Capitan.