RAW processing software,.....Which is the SIMPLEST program?

I think LR4 is easy to use ... provided you use it correctly.  It is, at heart, a digital asset management program and Adobe Camera Raw combined into one program.  It assumes you will import all your images into the program and manage them from there.  If you do that, life is easy.

If, however, you don't want to import all your images into Lightroom, then I can imagine LR4 would be a pain.  You might as well use Photoshop (or Photoshop Elements) ... or some other program.

However, I would highly recommend that people learn to use Lightroom as their sole photographic digital asset manager.  It makes life VERY easy indeed!