I upgraded my OpenBSD machines a few hours ago, and I'm still not entirely sure whether I notice any obvious TCP speed improvement. Then again, they're not really high-load computers. Maybe people with a higher throughput will be amazed.
FreeBSD is not really curious about being as portable as possible, I think. And it is somewhat larger, indeed, so it's not quite as easy to support more platforms.
I mean, are we surprised? Linux has on the order of millions times more users and funds (probably not developers though, but who knows). Thus, if there is any financial viability of a port I am certainly expecting Linux to "move" first. Rather, I am impressed that OpenBSD and NetBSD are keeping up as well as they do.
TCP stack is now running in parallel on multiple CPUs. Up to 8 threads are used to process TCP traffic.
That feels like it might be a big change.