As an enchanter, I do a lot of fiery enchants. They're okay, if you're looking for an extra damage kick. On Bloodhoof, depending on whether it's a good day on AH, they sell between 20-40g.

I found that fiery was prime for PvE as was icy on my rogue. Icy and crippling poison on main, fiery and instant poison on offhand. Depending on the price of mats, it really determines what's more economical. If you're twinking, I'd say go with +26 agility to your weaps, or maybe lifestealing for shits and giggles.

But if you're just looking for extra damage, I'd take fiery for the sole reason that it tends to cast more often than icy, even if icy is a bit cheaper.