Julian, I completely understand the desire to limit back ports, but TCK fixes are a bit of a different story IMO.
We are running the TCK tests against something that is not Jackrabbit. ModeShape is another JCR implementation, and we're currently using version 2.4.1 of the TCK tests on several different versions of ModeShape. We actually do have features that are written per the specification that are failing several TCK tests because of bugs in the TCK tests themselves. Running the TCK in trunk is not feasible for our Maven builds, and IIUC Jackrabbit doesn't publish SNAPSHOT into a Maven repository. So we're limited to selecting from the Jackrabbit releases.
Again, if the 2.6 release timeframe is about the same as 2.4.2, then we probably can wait for 2.6. If 2.6 is going to be a bit, we really would love to have these issues fixed in 2.4.2.
We really do appreciate the additional work on fixing these issues! Many thanks!