I had exactly the same Kev, I hated Arcane and loved Fire.... But after some convincing arguements from these Guru's on this forum I decided to give it a try. A IMBA change that was, cuz except for making cookies and tea us mages belong in the top of damage :)
My dps went up about 2,5 k dmg per second!
Now swapped some gear around and got 890 haste, and I am so **** quick with damage these days I can't belive it myself haha
Imba (quick) damage, doing 7k in Heroic 5-mans atm
Need only little hitrate wich leaves more room for haste/crit
12,6k dps on Twins, who wouldn't love that! Best fire nuke I had was 9k.
Scorching still possible as Arcane, so no need for a firemage to be in raid for a scorch-bitch.
More spellpower cuz of talents (about 250)
More Int cuz of talents
Usually lead the damagemeter
Manaflow, demands some timing with Mana-gems, using Evocation will stop dps for a while, but still compared to fire the diffrence in damage is insane.
U'll need a lot of haste, and a fire-mage prolly got gear focussed on crit.
No damage-over-time spell available (how I loved LivingBomb)
Just convince him to give it a try, and hopefully he will get excited when he sees his damage.