I have a priest alt getting close to 70. Planning on doing healing come Wrath. With the conversion to spell power should I be picking up healing gear or damage gear right now? How is, for instance, Spell fire stacking up against Primal Mooncloth? Is spellfire actually able to heal better right now in the beta? How about damage?
I strongly recommend hopping over to Wowhead's Wrath site and doing some research on how the numbers turn out. In most cases, DPS gear has better DPS stats (hit, crit) and Healing gear has better Healing stats. The spell power numbers are just much, much closer. In your particular example, the Primal Mooncloth Robe has more spell power than the Spellfire Robe, but it has mp5 and the Spellfire has crit. A DPS spec/class would rather have the crit.
A few weeks ago I covered the effects of the spell power change in Hybrid Theory, with some raw numbers to look at. You can read that over if you'd like, but I mostly just suggest hitting up wotlk.wowhead.com for specific items.
For more answers to your questions, read on!