Fun new feature I'm experimenting with: make editmode act more intelligently when subdividing faces.
In the first example, a sculpted multires cube gets all its faces subdivided. The sculpting is preserved with almost no visible changes.
In the second example, only part of a sculpted multires plane is subdivided. Again, sculpts are preserved, and there's very little change in the output.
In the third and final example, subdivision produces some triangles, which screws everything up. :) I've still got work to do.
Little story: I could not get this example to record properly; there were weird artifacts in the video. After scratching my head for a while, I realized that Compiz was turned _off_. Turning it on fixed the problem, and now video of Blender records properly again. So tell your friends: there's now an actual reason to have desktop effects enabled.