Anyway, 2.6.0 is out there now, and the patch from -test11 is a swelte 11kB in size. It's not the totally empty patch I was hoping for, but judging by the bugs I worked on personally, things are looking pretty good.
To give you an example, one of the nastier bugs that we chased for the last five weeks was a bug that could only be reproduced reliably on a 16- or 32-way system, and only when the system had flaky disks. Putting in known-good disks made the problem disappear. Similarly, compiling the kernel with another compiler made the problem disappear.
It turned out to be a really subtle bug wrt SMP ordering and stack allocation, and lots of thanks to Ram Pai for gathering all the information that eventually led to it being fixed. The fix was a one-liner and a big comment - but my point is that the quality of bugs has been pretty high lately, and we feel that we're in pretty good shape.
