He is a reasonable operator. Not quite as good as Pete Samu - who is actually very good IMO as a third jumper because he is very quick off the ground - but McMahon is pretty good.
My recollection of McMahon was that initially he was a bit so-so, but then put in 4-5 tests in conjunction with Hooper where he was very good at 8.
Personally I have no issue if he’s picked but no issue if he’s left our either. In terms of the role he’d play I actually think he’d be most similiar to Valetini. Not quite as physical, but higher work rate. But the fact that Swinton has been coming off and with his discipline issues in both the last two games it would seem more likely he is under the gun if anyone is.
If you ended up with a backrow of McMahon, Samu & Hooper on at the end you’d certainly welcome expect to lift the tempo.