They can be interesting, and 50 extra bonus points can allow you to make him or her much more capable, on a broad level then we are. A water aspect can be very useful in the west too.. but fire is the one who uses two short diakliaves with thier style. The ability to freely combo all reflexive charms, without actually needing to buy them as combos is very nice too, it means they have the constaint effects of essence flow, for all of thier reflexives... but there a few things about them.
Outside of sorcery and martial arts, their charms don't have the power of the celestial exalted. Their excellencies are limited to ability + specialty. When practicing celestial martial arts, invoking the form charm requires a MA + Dex roll, now, they can use essence triumphant(2nd Excellency) for that to make sure of it.. but that's extra motes spent.. the water heartstone - Kata-Sculting Gem is a better choice to deal with such matters. It costs more XP for them to advance their more mystical capabilities, meaning that in time, celestials will surpass them.