Those are probably the best TypeScript news in ages.

I've been working on this for a while now, was really excited when I saw the numbers. Was expecting them to be good, but they turned out better than I hoped.

admittedly I haven’t had enough coffee yet this morning, but it seems like from the description the biggest wins will come for monorepos leveraging many TS projects? Would a megarepo (one very large project) still be able to derive some benefit from these improvements?

it really depends on the mono repo. A mono repo where the dependency depth is very shallow ( many projects depend on a few common projects) might not benefit very much (the projects don't need to wait for each other anyway l, just for the initial common dependency projects). Mono repos where the dependency graph is deep will benefit a lot. In such mono repos there was a limit to the amount of paralelism available.