Cover Points

The first ever reviews (read "legalised challenges") of umpiring decisions in Test cricket has taken place. And Sri Lanka have piled up over 400 runs with 3 century scorers. Jagadish has a few suggestions, including a novel way of handling Jacques Kallis, and argues that there'd be less player dissent:

The one good thing that may come out of the referral system is that meaningless appeals could come down. e.g. if a batsman is struck on the pads and it looks fairly adjacent, previously there'd have been very vociferous appealing hoping that the umpire would ignore the obvious inside edge off the bat. Now, since the batsman can question the decision, such appeals would be reduced. You could also see less instances of player dissent.

Straight Point argues that the result of less pressure on the umpires will be even less reviews:

it will slowly but surely eliminate theatrical appeals used to pressurize umps...knowing at back of your mind that even if you get the decision in your favor, it will definitely be reviewed...

needless to say that this will definitely ease pressure on umpires and in turn we will see more good decisions from them...

hence resulting in less referrals...?

But, as Ottayan asks in the comments, what of the pressure that appeals put on the batsmen themselves? Kartikeya argues that the very first use of the new law by Kumble was absurd. How could the players have a better view of an LBW decision that the bowling umpire? After all, the players can't wait for a TV replay before asking for review. Also, on no-balls and improving the system:

Then there is the issue of the no-ball being checked by the third umpire when the review is made. Dismissals which occur off deliveries which are ruled as no-balls are not checked! If the third umpire were allowed to review decisions without prompting from either the batsman or the fielding captain, he would have identified that Mark Benson ruling a no-ball on a delivery where Zaheer Khan had Warnapura caught and bowled was wrong.

...

Cricket cannot afford to have players and umpires as adversaries. The referral system directly undermines the Umpires, and does so in the worst possible way. It ought to be scrapped immediately and if it is to be replaced at all, it should be replaced with a simple system where the third umpire is instructed to be in constant communication with the on-field umpires whenever an appeal is made by the fielding side and a decision is made by the on-field umpires.

And Samir Chopra comments on the Dilshan review. Do batsmen tend to misjudge snicks when their bat simultaneously makes contact with the ground?
Finally, Patrick Kidd has some comments on the now well-established review system in tennis, thanks to Hawk-Eye.