CentOS's kernel is a very old kernel comparing to many other distributions. The reason is stability but some times it gets annoying.
For example today i wanted to upgrade CentOS 5.2 server at work to 5.3. to make this process as trouble free as possible i cloned the server into another computer but once it booted , i noticed that it doesn't detect new computer's on board network card! and it was impossible to do the upgrade without Internet.