The more I work with this changed feature, the more unhappy I am with it! I notice now that you can’t select different items once you’re in the dialog…which means you have to re-enter the dialog for each set of items you want to align. Compare this with the SCALE and ROTATE dialogs, which do allow you to select additional objects and operate on them multiple times within the same persistent dialog (although, not all changes in selection…they leave the dialog if you try to select a completely new item…which they really shouldn’t do, BTW.)
SCALE and ROTATE do, however, support UNDO within the dialog.
I think all of these dialogs could use some improvement (I’ll write it up as a request) - but, at a minimum, the ALIGN/SPACE dialog should be brought consistent with the SCALE and ROTATE dialogs wrt how they behave in a persistent dialog.
[EDIT] I wrote up the request to improve all of the persistent dialogs and give them all the same behaviors in this Change Request thread.