That's very good. Now that I understand a cert can't have different expiries for it's domains, I can't imagine people having many problems with this.
Thanks for the excellent breakdown, both you guys rock.
Here's why I've been so interested on possible issues. I run my server out of my spare bedroom, and for years I've had no issues. This February just gone (two months ago) was the hottest February on record in Australia, and my air conditioner inconveniently chose to die that same month. The room where my server sits got over 40 degrees Celsius, and my hardware started to get flaky and write crap to the FS and corrupt files.
I'm still fixing issues introduced to the system from Feb, and as I type both my ownCloud and Roundcube domains aren't functioning (I think my PHP is pooched). Of course, I'm not using the --allow-subset-of-names flag at this stage, but if I was and the client tried updating now, I'd probably lose two of my three domains.
This is an extreme example and hardly representative, I just wanted to make sure I had an accurate picture of the new flag in my head before I considered using it in the future!