I have not used one,I have seen them in Cabela's they look great for varmit shooting,I don't carry rests.I used to have one of those Bi-pods on my 25-06 but I only used it once in 6 years.If I have to shoot a long ways I just shoot prone or from my knee,or some form of rest.
I think alot of pepole put to much into shooting sticks and rest when they should practice good'ol shooting positions,they are way quicker than setting up sticks,IMHO.