I frequently carry a set. Monopods are worse than nothing at all - they seem to actually increase movement. The bipod type are what I've found to be beneficial. And like others have said - rest the forearm on them not the barrel.
My current set has to be adjusted using the little flip levers. That is slow (cost me a hog last year). When I go to buy another set, I'll get the kind that has the adjusment build into the grip.