I'm 2 levels away from Incinerate and I've been pondering the usefulness of this spell compared to Shadowbolt. First, let's see the stats on the two:
Incinerate (Rank 1)
325 mana
403-467 Fire damage (+100.8 if target has Immolate on it)
2.5 seconds
Shadowbolt (Rank 10)
380 mana
482-538 Shadow damage
3.0 seconds
If you have Immolate on the target Incinerate seems better, with higher damage and lower mana cost, not to mention lower cast time. But I don't use Immolate that often. Well, now I do, because I'm Destruction spec'd, but otherwise I would settle for Corruption and Drain Life with a Shadowbolt tossed in there for good measure.
My first impression was "Sweet, a faster Shadowbolt!" and then "Uhm, but I don't use Immolate," and then "Ooh, Destruction plus this owns!" and then "But with Destruction my Shadowbolt is just as fast."
When do you use it, why and is it good?