I think cs3 will have a higher learning curve than pse, but it is way more powerful. But... Ask away in the forums for either program, and we all can chime in to make your transition easier. Sometimes, once you figure out the basics, then any of the programs become a joy to explore.
Also, don't forget to check out SBB's ezine. There are some really special tutorials in the ezine. Here's the one I did for PSE for December:
Click here for EZINES
December is not yet on store shelves. But there some really good tuts in the previous months too (not to mention the great articles and downloads)!