David Megginson wrote:

On mailing lists,
I've actually had violent reactions from otherwise experienced and
competent pilots when I casually mentioned that pressure altimeters
are routinely off by hundreds of feet at cruise altitude.

It's pretty simple, really. It doesn't matter at all if your altimeter is off
by hundreds of feet at cruise altitude if everybody else at that altitude has
the same error. It would be possibly unsafe for you to set your altimeter
accurately when everyone else is setting it to the broadcast local altimeter
setting.

In short, it doesn't matter. Just do it like everyone else. For noise abatement
reasons.

George Patterson
A man who carries a cat by the tail learns something that cannot
be learned any other way. Samuel Clemens