Wordpress upgrades to new versions it typically a simple matter technically speaking.  Unless your hosting situation prevents it it’s usually just a few clicks.  The real issue is one of your upgrade policy.  Some people prefer to be on the leading edge and always upgrade right away as soon as something is available.  Some people adopt a “wait and see” approach and wait for the new version to be really burned in before they use it.  As with all things of this nature we recommended doing anything like this in test mode before changing anything on your production system.  We also recommend being somewhere in the middle of the two extremes.  Wait a week or two and read the general comments made by others and then make your plan.

In the case of serious security breaches or holes you may need to act fast and may not be able to wait a week or two.  You need to set your own policy and then act accordingly.