>
The code is some of the most efficient and widely used.Efficient, yes. Throughput in general is not a problem.
Widely used, well... yes to that too. Although in this regard I would attributed a good chunk of it to inertia. When (common) use of cryptography started to take off around the time of the browser wars, there weren't too many options around. Web servers needed a way to serve protected content, and there was OpenSSL.
Not just available, but already supported by language bindings and relatively easy to set up thanks to mod_ssl.
First mover advantage + network effects + the fact that getting crypto right is really hard. If you wanted to unseat OpenSSL, you would need to overcome the fact that despite all the bad rap and the butt-ugly, and the leaky API, it was still getting the most exposure and field testing. Unlike some newcomer library, OpenSSL has the advantage that it is firmly embedded in the software ecosystem, and it has benefited from more than a decade of bugfixes. (I still remember when the timing attack for extracting RSA keys was discovered. The bug was pretty much everywhere, and not just in OpenSSL.)
The widespread use of the library boils down to a simple and womewhat depressing fact: OpenSSL is used everywhere because OpenSSL is used everywhere.
Replacing it with something better will be a long uphill battle. Any newcomer would need an aggressive test suite which covered EVERY known implementation bug. And a sane API. And a project with the political savvy to succesfully lobby for its use through all avenues.