Yeah, I'm waiting to read some first hand reports from people who have installed them. There has been some vague reference on another forum about needing to have the bolt milled (I'm sure they meant the carrier), but nothing specific.
Edit: I was wrong; saw some pictures and the bolt head itself gets a groove milled into it for this mod, which extends well into the bolt face. Not to mention the machining of the receiver itself. I'm not really sure that I care for the bolt alteration.