Re: What?
Updating your kernel will basically never affect any of your existing software. It will rarely make it so any new software will run (perhaps there could be some software that relied on a particular new kernel feature). Kernel updates are much more likely to affect hardware compatibility than software compatibility, and that's most likely to mean a piece of hardware that didn't work will start working.
Updating your C library has the potential to affect your software, but between the software developers and the maintainers of glibc, they do a good job with backward compatibility. I've never had a program stop working after a kernel update or a glibc update. Even programs that you manually installed on your distribution will almost always continue to work after a distribution upgrade.