Apple's new OS (Mountain Lion) came out last week and for most the upgrade has been well received.
However, we always tell our clients to patiently wait at least a week or so to upgrade mission critical work comptuers in order to be sure it will work for YOU.
Before any upgrade, you want to be sure that your critical applications are compatible BEFORE you upgrade. Just ask all the folks with Quickbooks who locked them selves out of their data by upgrading to Lion before they checked compatibility. As with the Lion upgrades, there is a great web site to research your app compatibility prior to upgrading.
Please check out the very nice (and searchable) compatibility list at Roaring Apps to get a feel for whether it is time for you to upgrade to the latest Apple OS. You should also look at Apple's website to determine if you machine meets the minimum requirement for Mountain Lion.