Rolling restarts are happening this afternoon on all US realms that do not yet have voice chat enabled in order to enable voice chat. I can only presume that voice chat is working well on the 42 realms it's currently enabled on, because Blizzard is adding the remaining 183 realms to the service en masse. I can't personally comment on the quality of the service, as it has not yet been implemented on any of the realms I play -- but if this round of restarts goes well, we'll all know by tomorrow. Drysc's original thread about voice chat has been updated with the list of realms that will have voice chat enabled today and Nethaera chimes in to clarify that, yes, this is all remaining realms. Restarts are expected to be finished and all realms back online by 2:00 PM PDT (that's 5:00 PM EST for you on the opposite coast). So if all goes well, expect your realm to be back up soon.