BIG-IP Acceleration Tab, What is it?

It's mainly a logical grouping of features that focus on speeding up your applications. If you are licensed for the BIG-IP AAM (Application Acceleration Manager), then you'll see a lot more than if you just have LTM.

If you just have LTM, you'll see some of the same things you see under LTM - Profiles - Services section. Things like HTTP compression, TCP profiles, SPDY profiles.

The rate shaping functionality has been moved under here as well along with the iSession (tunneling between F5 instances with basic WAN optimization) is set up here as well.

Overall, if your licensed features didn't change by you buying something new, then it's mainly a grouping of features in the GUI as opposed to any new major functionality.