It would be a shame to lose it if the reason was that it wasn't 100% reliable. All of my verified common ancestors / thrulines were correct. I did find a few of the shared matches coming up with what appeared to be a rogue "mother's side" when the match being shared was a definite "father's side" (and vice versa). But these were matches with no tree or not enough of one to verify that Ancestry had actually got it wrong. I do have one definite "both sides" (assigned by me), possibly if I had pursued those two lines, I could have rationalised the apparent rogues. But with all Ancestry's assignments gone now, I'll never know.