The tech note ( which I found after I started the upgrade, as the release notes point you to somewhere that doesn't actually have the tech note) says that "....where possble subscribers are upgraded in parallel...". I've just fired up the upgrade tool for 6.4 -> 6.5 and selected both the master and all the subscribers. I'm currently waiting for the master publisher to come back before upgrade of the secondaries starts.
I have to say that having a default of upgrading all secondaries in parallel is, I think a bad idea. Granted if you read the tech note, you'll just upgrade some of the secondaries at a time. Hoerver, like me, some people are going to select everything and click upgrade. Luckily I've still got our old AAA solution as a backup so if all our secondaries do go down at the same time auths will fail over to the old solution..... I'm waiting with baited breath .......
Perhaps a dialogue box saying that all the secondaries will (possibly) restart at the same time might be in order ?
Or a user selectable option to let you decide whether to upgrade secondaries 1 at a time or all at once.
Rgds
Alex