Here is some more info from Steve Kass. He paraphrased Microsoft's internal response to the confusion about who should install 3054 and who should install 3159.
3054 includes the new fix along with a few important general-release fixes since SP2. But 3054 doesn't include several quick fix updates that weren't general-release, but that some customers have needed and installed. These latter customers can't install 3054, because it doesn't have the newest quick fixes they need. So they get a different build–3159–one that contains the newest fix, and also contains the post-3054 quickfixes.
Build 3159 isn't for everyone just because it contains more fixes. The extra fixes it contains were not tested (maybe not even designed) to be general-distribution fixes, and it would be risky if not a plain-out bad idea to distribute them generally, along with the current critical fix.
Steve Kass told us a short while ago that there are two new hotfixes available to finally correct the maintenance plan issues brought about by SP2 and all of its descendants.
If SQL Server is between 3042 and 3053, get build 3054 from http://support.microsoft.com/kb/934458
If SQL Server is between 3150 and 3158, get build 3159 from http://support.microsoft.com/kb/934459
Why everyone shouldn't just move to 3159, I'm not sure. I'm not quite ready to try it out yet, but they must be pretty confident this time, because they're pushing out through Windows Update as critical.