Yeah. The boiler lid on wood mod/ custom machines has a plastic thread, which is good and .... Well .... Better than wood would be.
the plastic part of the drip tray is a kind of brittle plastic. I had mine replaced fairly early on due to a crack which I think appeared after washing it in too hot water. ( I only wash the replacement in cold now).
i think pre the machines having the plastic insert to the drip tray there was nothing - just a grill . If this is true > rust city!
I'm afraid I wouldn't know about metal quality, except that mine has served me well.
to me the main problems with Pavoni levers are not so much the manufacture as the problems that may arise from uncaring use. Ie: Don't let water pool in it, or around the edges after you have temp surfed & sent water spraying over the bench!
Oh yes, the ends of the plastic that covers the sight glass on mine has gone from clear to white over about 18 months. Looks fine though & doesn't effect performance.
Hope that helps!