The evolving standards test is a bit silly but it's the test that has been long used in these cases. It works for something of this nature WT notes his reservation is partially caused by Orin Kerr.
As far as Kerr, I realize that many professors still have an antiquated and wrong view of defense attorneys. I have personally sat through lectures where professors hinted at defense attorneys being nothing more than slimy drunkards who will manipulate the law in whatever way as long as they get the guilty off.
Kerr, quite simply, is wrong with his opinion of this opinion. It's unfortunate that he is not willing to recognize that at times justice can come out of the halls of injustice with the Supreme Court. It happened last year with Washington v. Crawford and this year with Roper v. Simmons.
UPDATE:
Upon further reflection on this case and Professor Kerr's post, I think that my initial reaction is incorrect. This isn't actually an ethically area, however, I think that if defense attorneys follow this then it will create further disdain in the public of defense attorneys.
However, this isn't the fault of the Kennedy opinion. It is the fault of the evolving standards test that is not a good test. It is also the fault of a system where lives are exterminated. Any defense attorney worth his bar card will fight for his clients life as far as possible. This means that there will always be delay in the death penalty regime.
This isn't an incentive created by Kennedy's opinion. It is an incentive created by an unnnecessary death penalty regime.