You can download the public beta for Photoshop CS6 from Adobe as of Thursday morning just after midnight. This means that release of the final product is not far off.
Every time Adobe releases a major version upgrade the question is whether or not it is “essential” to upgrade to the new version. Two things make this an upgrade you will want to make. First is the possibility of policy changes by Adobe on upgrading versus purchasing a new license for the product. In the past upgrading was not an issue if you owned almost any previous version of the software. That may not be the reality of the future as there was talk that even this upgrade would only honor one version back. They have softened that requirement for the time being, but I suspect future upgrades may be limited. Currently, you can upgrade from CS3 or CS4 to CS6 anytime before the end of 2012.
Perhaps even more important is that this upgrade includes substantial improvements in performance, improved quality of results from many tools, and a completely new raw engine that will amaze you. If you have already jumped on the release of Lightroom 4 you will be aware of the new raw controls. The interface has a new look as well.
You can download and start using CS6 now by getting the public beta, but you will have to purchase the upgrade at the end of the beta test period or it will stop working for you and you will be back at your previous version wishing you had all of those great tools to work with.