I'm actually on the fence about Retrobrite. We all know that plastics will yellow with age and this is a normal progression for various models of computers.  In terms of the Retrobrite process there are two sides.  On one hand, it looks nice if done well but on the other hand, it is available to do so why bother?  I'd rather an even color as opposed to a computer that has one side darker than the other.  For me, those are worth Retrobriting.  Just my 2 cents.