There is at least one thing you don't get in PSE equivalent of PS/CS and that is curves. There are 3rd party plug-ins, but the one I used to use was not very good (Human software curves 1.6) and could only be used at low opacity as a filter.

PSE4 does process RAW, but not in my opinion as well as the dedicated Canon (DPP) or Nikon (NX) alternatives.

The other thing about PSE4 that I suspect is worse than genuine article is the Preview quality. That is the main image presented is widely different from the one that returns after you save it. It is not obvious, but all software displays during processing ARE only a preview.Having spent a long time editing and then finding the saved image has far more noise and 'artifacts' in than appeared during editing is a serious drawback and one of the reasons I am a PS unfan.

There are undoubtedly a lot of things PS/CS/PSE does that other programmes don't do and as far as I can tell everyone (including me, though never since getting NX) does at some stage pass an image into PSetc for a final add or twist. That is however very different from using it as one's mainstay and paying the price for the full version.