We evaluated PolarSSL at FoundationDB while adding TLS support to our 2.0 release. In the end I think our primary deciding factor was a lack of support for hardware accelerated AES-GCM using AES-NI and PCLMUL on modern hardware, although I understand they are working on it.

The library as a whole was relatively well documented and pleasant to use. I am not going to even pretend to be enough of a crypto expert to have my own opinion of its security quality, though.

EDIT: I suppose I should add, for completeness, that we eventually decided to use GnuTLS for our TLS plugin implementation. Just in time to catch the latest GnuTLS security problem, but we avoided heartbleed.