[exim] Experience using cutthrough delivery

I was wondering if anybody has experience using cutthrough delivery for
large-scale exim deployments.

I did some initial testing of the feature before flipping the switch, which
uncovered a number of bugs. One of these bugs was already fixed in the 4.90
release, the others I just reported (bug 2229, 2230).

Considering this feature has been around for nearly 6 years, I was a little
surprised to find issues. Is this feature used in production settings?

Thanks,
Todd