Since The Dragon Aspects have had a strong presence in every iteration of WoW so far, the August Celestials have big shoes to fill. Are they as interesting to you?
Though the origins behind the Aspects and the Celestials differ (with the Celestials being closer to the Ancients), they fill the role of somewhat passive demigod that was formerly filled by the Aspects. I've always been a big fan of the Aspects up until the ending of Cataclysm. Didn't care much for the sudden loss of such 5 iconic characters at one time. Really 6, if you consider the fact that Thrall has zero presence in Pandaria.
But the Celestials, thus far, don't hook me quite as effortlessly. There is also something unsettling about the chosen voices coming from gigantic idling beasts. Chi-ji, for instance, stands constantly quacking whilst his calm young male voice comes out from seemingly nowhere. Same with Yu'lon, whose voice is alarmingly saccharine and unnervingly positive despite the immense chaos going on around her (and that her tongue wiggles around in her unclosing maw).