One good way to know which actions are important for you is to work on another computer without any action added... That is my case now. The old hard disk died... I had to buy a new unit with Vista and reinstall PSE. Luckily I had saved data and software installation files on an external hard disk.
I can tell you I was very frustrated not to have layer masks. Of course, I know how to hijack the mask of an adjustment layer, but that is tiresome. So, I had a look at my external harddisk, and decided that the easiest and more efficient step was first to reinstall the 100 hiddenelements tools for PSE4 (which have always worked for me in PSE5 and PSE6...) No big problem, since I had saved the atn, png and xml files to keep the actions in their own categories. I just searched this forum for a link to Richard Lynch's installing instructions for Vista. Once those files copied in the right Vista directories, I started PSE6 without deleting any cache files. As I expected, there were signs of background activity, so I waited for 5 or 6 minutes. When I opened the effect palette, everything was there in its own category!
Now, depending on what I can find on my external hard disk, I can reinstall Graffi's effects and my beloved plug-ins, Neat Image and Ptlens (the equivalents in PSE6 are not bad) as well as smartcurves.