This is a good spell to start fights at lower levels. Untalented and used against a foe with no speed boosting abilities at max range, you can cast 3 Lightning Bolts in the span of time it takes for a mob to reach you. You can even cast a shock just as the third Lightning Bolt finishes casting to max out damage against a pulled, incoming mob.
It is also more likely to use during combat because of its 2.5 second casting time as opposed to other classes' similar function spells and is fairly mana-efficient.
Patch 4.3.0 (29-Nov-2011): Lightning Bolt has a new spell effect.
Patch 2.3.0 (13-Nov-2007): Cast time reduced to 2.5 (from 3.0 where applicable), mana costs reduced, benefit from spell damage have been modified to maintain the DPS of the the previous, longer casting time.
Patch 1.11.0 (20-Jun-2006): Mana cost reduced approximately 17%.