I got a chance to play around with the Celestial Power set on my lvl 16 character and I must say the power set is pretty much a very support intensive power. Which basically means it's a power you want to get if you want to play a pure support role character with your friends. First and foremost I'll come out and say that trying to solo with pure Celestial Powers is stupid. The developers themselves said it that the power set is pure support. There's just not enough DPS in it to kill villain (and above) packs, in fact you'd probably get severely hurt soloing henchmen packs with pure Celestial powers. Don't even bother trying to solo a single super villain because you'll just get trashed. What the Celestial power excels at is as party support. Many of the celestial powers have some sort of healing factor attached to it (the powers act differently depending on what you are targetting). If you are targetting friends and allies it becomes a healing/buff power while it becomes a damaging/debuffnig power when you are targetting enemies. You also gain energy by healing your friends and allies. Soloing with Celestial powers is viable if you take up another primary damaging power set while using the celestial powers as secondary/backup powers as this makes your character more balanced and soloable but being party support is where this power set shines the brightest.