From a CDN perspective, whats missing is there is no kernel stack on FreeBSD / Linux, and no support for sendfile/sendpage and no support for segmentation offload entirely in hardware. So you can't just send an entire file (or a large range) and forget about it, like you can with TCP.

Some NICs, like Broadcom's newer ones, support crypto offloads, but this is not enough to be competitive with TCP / TLS. Especially since support for those offloads are not in any mainline kernel in Linux or BSD.