Had the situation only once in anger - but had it briefed beforehand. Flying PIC with a pilot friend who hadn't flown in a long time and was not current on the model. We did a multi-leg trip and this was to be his landing.
Briefed beforehand that if I didn't like what I saw, it was going to be the standard callout 'my airplane' and I would take over.
Approach went reasonably well, but he was a bit too fast and couldn't handle the x-wind well. We were on our way into the grass when I made the call, took over and landed. No hard feelings, we discussed the techniques involved (or rather, the absence) afterwards. And yes, we're still friends and go flying together!
On a different note, once 'helped' the father of a friend, who has a license but isn't very current, by very gently applying a bit more back pressure on the yoke for the landing from the RHS. Turned an 'arrival' into a greaser. Happiness all around!