We all have to rest our rifles when we make long shots. Harris bipods and a rear sandbag do a great job for many styles of hunting and types of rifles, particularly prone shots.
There are some hunts where Harris's are a little too cumbersome, catching on vegetation or just not high enough.
I have been shooting off Underwood shooting sticks for several years and consider them a great tool. Light, quick to setup, very reliable. Stoney Point makes a similar set of sticks.
Recently I started carrying a Stoney Point telescoping bipod called a Polecat, and the more I use it the more I like it. The Polecat is a little bigger and bulkier than the sticks but it will also do more. I really like it for sitting shots, where vegetation eliminates prone shooting. It is extremely sturdy, quick to adjust and useable as a walking staff. The ultimate set-up is to put the Polecat on a 25-45 degree angle under the forend and a set of sticks angled in the opposite direction under the buttstock. I can take my hands right off the rifle and it does not move at all.
Alternately I found that if I can get my back against a tree or brush I don't need the buttstock rest. I like to take an analytical look at the crosshair movement when I set up on these field rests - the Polecat is allowing a very steady hold from the sitting position - virtually no movement at 100-200 yards if you do your part. We are making hits on large
Polecats and sticks are not for extreme range but I have found them to be good hunting tools for out to 600 yards for my rifles and ability.