Here goes...Methinks this R vs. SAS debate is less about the merits and demerits of the two software and more about the David vs. Goliath(or Hare vs. Tortoise) effect. David, in this case also provides strong competition in a slightly monopolistic market situation.
I have worked with SAS and I don't have a strong opinion against it(except for it's really bad graphics). I am new to R and I like it(yes, there will be some pet peeves as time goes by). I have also used most other competing software in this space(SPSS, Minitab, Stata, Matlab etc).
So what's the issue you may ask? Well, no matter what anyone says(or posts), I believe one of the main reasons that R is generating such a lot of press(and don't get me wrong-it has strong merits) is the fact that with all it's merits it is also FREE! Whether we like to admit it or not, it bothers us that we have to pay for using SAS when R which is as good(if not better in some areas) is available for zero cost. Would the same debate be as heated if R did not deliver? I doubt it.
Add to this the point that R comes in as the 'underdog' that most of us like to see win and you get a better idea of why there is so much angst all around on this issue.