One of the major improvements here: this finalizes the license change to Apache 2.0, which makes OpenSSL finally GPL-compatible. That removes one of the major reasons people had to avoid it.
(Specifically, OpenSSL is now compatible with anything licensed "GPLv3", "GPLv3 or later", or "GPLv2 or later". It's not compatible with "GPLv2 only", but that's a relatively small amount of software.)
Other major improvements: TLS1.3 support, Linux kernel TLS support (hand off crypto to the kernel and then read/write as though you had a normal file descriptor and let the kernel handle the crypto), and opaque low-level structures (no more dependencies on OpenSSL internals).
(Specifically, OpenSSL is now compatible with anything licensed "GPLv3", "GPLv3 or later", or "GPLv2 or later". It's not compatible with "GPLv2 only", but that's a relatively small amount of software.)
Other major improvements: TLS1.3 support, Linux kernel TLS support (hand off crypto to the kernel and then read/write as though you had a normal file descriptor and let the kernel handle the crypto), and opaque low-level structures (no more dependencies on OpenSSL internals).