setjmp/longjmp is essentially what exception handlers do for you. I love C for its simplicity, but I'm not certain that leaving exception handling out of the language was a good idea. There are a lot of people who would agree with me there, including (I believe) a few Bell labs veterans who wrote the language in the first place.
The nice thing about exceptions beyond setjmp/lngjmp (in C++ at least) is the destructor semantics which you can use to guarantee that resources are cleaned up on error. There are better ways to handle such things, such as scoped resource allocation, but exceptions do an ok job.
