Even better than a 'Slicer' is a 'Master Smuggler' as Masters receive a 5% bonus.
Slicing a weapon will increase either the speed or the damage, but not both.
Slicing armor will decrease the encumbrance or increase the percentage rating of the resists listed under 'Effectiveness' for that item.
Locked containers can be sliced open, but very rarely have anything noteworthy inside.
If a smuggler cuts the wrong wire, the weapon or armor is not harmed, but it cannot be sliced again and has no increase in stats.
If a container is mis-sliced, it will remain locked forever.
I hope this helps.