This can sound odd from me, that since my early days of OOP programming have always advocated the use of such qualifiers. The main reason I liked such qualifiers, and the main reason I presented to my students when teaching them OOP, was that the resulting code would be easier to read and, most notably, a lot of IDEs will bring up popups and code helpers to show you available completions. In other words, simply typing "this" will activate a popup that presents you with a list of choices between methods and fields to place in.
So what did change my mind? Why am I now advocating to avoid the use of qualifiers? Well, it is really simple: I switched back to some C code, and found myself comfortable while writing "unqualified" code. So I thought that in order to keep code clean and to get a more coherent syntax, avoiding qualifiers can help.
As an example consider the following piece of (imaginary) Java code:

   this.description = this.computeANewDescription();
   this.setTimeAndDate( super.getTodayDate() );
   this.setStatus( Status.STATUS_OK );

Now the above code can be rewritten in the following way, assuming you also use static imports:

   description = computeANewDescription();
   setTimeAndDate( getTodayDate() );
   setStatus( STATUS_OK );

Isn't it really much like a C code snippet? Apart keeping your fingers relaxed, due to not extra-typing keywords, the code is much more clean and can be read by any C developer.

The article Avoid the use of this, super and in general class qualifiers when not stricly required! has been posted by Luca Ferrari on September 23, 2011