Hi Kimmy -
Here's the answer.... (now that you know what backup does AND you have tested it)
A. there is now a 1.8.1 - I would say unless you know of an issue, and things are working fine - what's the point? You do have the right idea about reading up on changes, unless there's something compelling - its just more stuff to do. BUT - it is fun, that is at least in part why I do all this stuff.
B. You can use the lampp backup feature to backup virtually everything thing from a current version of LAMPP. move the backup shell file to another location.
C. lampp is different than Windows XAMPP because the Linux operating systems have features that support 'diffing'. The 1.8.0 to 1.8.1 upgrade is a diff/patch. It leaves things in place and makes selective changes. It can't fix thing like elaborate configuration changes, but a 'stock' 1.8.0 lampp can be 'transformed' into 1.8.1. There is one caveat, although it 'de-links' old parts that are not replaced directly, it does not remove them. Anything with a 'new version' will be over-written.
D. You can also do a traditional re-install, where you get the backups manually (export databases, copy files etc.) - then install clean. In this case you can't use the lampp backup, because it only works with the same version it was created with.
E. Noting that last comment - IF you have a lampp backup and have tested it - you can upgrade safely. In the worse case you simply remove the new version - re-install the old lampp version and use the lampp backup shell file to restore.
F - Caveat - test this first. There have been folks who could not get the backup to work. At some point you always have to 'push the button'. I have (on Fedora 15 &16) used both methods, and have re-installed with a backup successfully.