Pros:
Redistributes pack weight
Improves balance when traversing water, mud, stepping over things
Really helps with elevation
Keeps arms pumping (for me I find without I had a lot of swollen fingers on long days)
Can be used with your tarp as a tent pole.
Cons:
More gear to buy
Can be bent or broken if something falls on them.
If used outside of backpacking you will look like a dork
Overall major help. I don't think they are necessary on a short hike, day hike, etc. but if you are back packing for any significant length of time it's a handy thing to have. You can absolutely go find a stick but if you're constantly out there want the benefit the consistency of always having them available is big deal.
