Composer 2.0 is now available
Massive improvements in terms of both speed and memory usage with new Composer.
The difference depends on your use case, so while I've seen reports of improvements of over 50% to both in some projects, I cannot put an exact number on it.
As a side note to this, require/remove and partial updates are now much faster because Composer will now only load the metadata of the packages which are being changed.
