Personally I believe C is the best language to develop in. Anything you write in C can be easily used in any other language you care to use; this characteristic is not true for any other language you could name.

There is nothing wrong with developing security-critical code in C if you're an experienced C programmer and know what you're doing. The GnuTLS programmers were neither experienced C programmers nor knowledgeable about security; they should not have been writing security-critical code in the first place. And no one should have ever believed that their code was trustworthy.