Hamish,
Getting back to your original question, I did find they have fixed more things in the stacks than just the count. They also seem to have fixed the "remove from stack" and "split stack" problem that has been discussed on the forum. It was more of a cosmetic problem than anything. On a negative note, I did notice some horizontal artifacts in develop mode when zooming to 1-1 view and draging with the mouse before the view was clear. Zooming in and out cleared up the artifacts. I restarted lightroom and cleared the raw cache and so far so good. These are CR2 files, not DNG as there was mention of a DNG artifact problem being fixed in the release notes. I will repost if they come back!