While in the process of building a stirring system for my Mash tun, I read thru old posts and it seems like a new survey might be in order. Obviously, there's time and cost associated with adding a stirring, RIMS or HERMS so the focus should be on results or expected results of this investment. Guessing that those with isolated, insulated tuns won't see the value of stirring the mash, but those with the option to add heat and/or step mash would see some benefit if nothing more than consistent temperatures in the grain bed.
I used a drill motor (incl. an old satellite mount) and mud mixer to add continual stirring to my tun. I trickle heat thru a gas burner and add blasts to rectify any large temperature fluctuations as well as when bringing the mash up to the next temperature step. I was getting huge temperature gradients thru the mash prior to this latest improvement.