To add to the con's;
-An extended length brake line is required,
-you will need to install travel limiting straps,
-you will need to carry a small length of chain in your rig just incase you have to jack it up to change a tire,
-and they look hella scary when ascending or descending a steep hill.
..and now the rest;
They definitely add to suspension travel, but unless you have a selectable locker this won't do you a bit of good for traction (at full droop),
Carry a spare 1/4 leaf or a spring shackle if you happen to snap one, I've seen trail rigs limped off of a trail with a busted 1/4 leaf due to over extending and not having a way to reinstall the shackle onto the original frame mount.
Just my two-cents worth.