[URL="http://www.wowhead.com/spell=55360"]Living Bomb[/URL] can be cast on the move, so very useful for situational fights, and if you take the [URL="http://www.wowhead.com/item=45737"]Glyph[/URL] the DOT ticks can crit. It can also set off [URL="http://www.wowhead.com/spell=44448"]Hot Streak[/URL] if the ignite crits, giving an instant [URL="http://www.wowhead.com/spell=12505"]Pyroblast[/URL]. Oh, and it can be used on multiple targets at the same time since patch 3.2. The damage you can do with them all going off one after the other is immense if you time them right and the RNG gods are kind. Don't forget when using LB to let it ignite first before you reapply it. Addons such as Mage Nuggets will give you a warning before it goes off, or you can use Power Auras to set up one yourself
There are two things to watch for if speccing fire:[LIST=1][*]Be careful to watch your aggro. With such a lot of burst damage the aggro can creep up on you and you suddenly find every mob chasing you instead of the tank. Klog had to save me more than once when Pryderi had a fire spec[*]Fire spec is more dependent on the RNG than any other, so one day you'll be top of the DPS by a long way, the next at the bottom
[/LIST]I have a macro for the times that I used to take aggro:
"/s Noooo!!! Take the Healer instead!!
/cast Ice Block"
From what I have read Fire will be the best spec for raiding come Cataclysm. Its so much more fun than Arcane, the spell effects are awesome, and a mage isn't a proper mage unless he can throw out huge fiery balls of death.