I believe the manufacturers of Hawkeye say the prediction part is 95% accurate. You are never going to get a technology that is completely and utterly perfect. What you have to do is put your faith in the best technology available. There were several bad umpiring decisions in the England v India Test series that DRS would have sorted out. Until they start using DRS, I hope India get some absolute stinkers in every game they play.
Even if hawkeye isn't perfect, and there are mistakes now and again, the frequency of such mistakes is FAR less than that of a human umpire's eyesight. That alone justifies it's inclusion to me.
I also hope sides which refuse to use DRS fall victim to some absolutely shocking umpiring.
India have gotten a fair share of stinkers, and Sachin has always been in his career the Umpire's fav bunny, especially steve bucknor, and I remember Ganguly given out LBW once by Asoka De Silva, for a perfect forward defense, off the middle of the bat, and no one likes those.
However, I am as much against those decisions as I am against DRS. All these 95% stats or 'FAR less' stats are meaningless when they are based on what Hawk Eye itself is saying.
As I wrote above, if a student (hawk eye), is asked what is the capital of Australia and he says Adelaide, and you just go by whatever he says, then the student is naturally going to be right a lot of the times, even when he is wrong.
Also lets face it, the manufacturers of Hawk Eye are always going to push up the numbers when it comes to accuracy. They are never going to say, yeah we have no clue what we are doing.
Hawk Eye just doesn't have a clue. Especially if what
@Davoo said is right -
Ajmal himself said the ball he bowled was a doosra and the ball is spinning like a normal offspiner (in hawk eye graphic).
Atleast a human umpire can tell the difference between a ball that is a doosra and that is an off spinner, and which way it will turn. If the Hawk Eye cannot even tell the difference between two different types of deliveries, and which way the ball will be turning, then its just ridiculous, and should be thrown out immediately.
Yes no one likes wrong decisions, but DRS is not the way to go about correcting them. Involving DRS itself has led to some shocking decisions, especially all through the Ashes last year.