Is Shimano aware of your particular case/set up? that is critical in how to evaluate their response. Or your store? DA has 3 years warranty, the entire DA system.
One of the venues Shimano is pursuing in my case- and the effort and turnaroud time are outstanding, is the shifter.The 9000 vs 9001 shifter articles, etc, the 9001 was redesigned similarly to Ultegra 6800 but with a better, less dragging cable routing. Reason they are pursuing this with me, is that, if indeed my particular 9000 is suffering from the cable routing issue (off sync etc), the highest gears that can be off sync could be are 18-21T- which would coincide with the carbon cluster. The reason grinding would be less heard on 23 or 25 are physical, as the disks are big enough for the chain to not be too close to the lower cog and grind IF THE SHIFTER IS DEFECTIVE.
One could therefore have a bad combination of AN OFFSET shifter keeping the chain between gears in the central portion of the cassette, the soft carbon spyder cogs. But unless the problem is evaluated, not even I can be fully sure it is the casette if indeed my 9000 shifter went bad two weeks after installation.
One thing that came out of my situation, is that, although I thought my DA9000 was shifting fast, it was not- not compared to other 9000s. i thought it was. So off the bat, there is some lag in the shifting unit.
I also heard that editors from BikeRadar are aware and are also following up the issue. With Shimano. From a media perspective, awareness is out there.
As such, I do not recommend legal venues particularly if Shimano has not had a chance to fully evaluate the defective systems on a case by case basis. There are, out there, thousands of DA casettes with DA9000 that never creak or grind. At the same time, some DA9000s had some issues and 9001 arrived late 2013 and this year. Case and point- I never had this issues the first two weeks (900 kms). So did the casettes suddenly go bad as i gained power (and flexed and droped the chain) or did my 9000 fail, off-synced those cogs, guaranteeing the problem or a chain drop under load?
All the aspects must be investigated. In my case, everything except the shifter and derailleur has been investigated and changed.
SRAM: no doubt the spacing on the SRAM, as well as the one piece construction, may help alleviate the noise on those cogs. But the casette is as expensive, nearly, as a new shifter. And the cassette could mask a defective shifter only due to better construction, but the shifter may still be compromised.
If checking the forums, one will find some type of anoying issue with Super Record, SRAM Red, etc, issues affecting a small percentile of users. Most times, Campy and SRAM and Shimano improve their product to solve those issues as well. But if 90% ort more of the delivered system work to spec, that perhaps meets the industrial QC. We may be ones of the 10%.
Will update this forum once I have a few hundred kms on the 9001.