Elements 4.0 vs. Photoshop
If you really are not proficient with PSE then you probably won't find learning PS to be that much harder. Photoshops primary adjustment features are easy to use and there is a wealth of Photoshop help online. You can google most anything that you can think of concerning photoshop and have pages of related info immediately. It takes a while, but once you really start to understand the flow of Photoshop you really start to feel empowered, and when you read in the various Photo Magazines about how the pros edit and manipulate their files they are all talking Photoshop and this alone is a good reason to learn Photoshop.
Happiness is that one shot that you can't find fault with.