Seeing as how this is an old post, I figure I'll throw some updated info in...
Even pre-WotLK, you should hit-cap as you acquire gear (i.e: quest gear, badge gear, etc.) According to a couple sources, FFB mages' +hit caps at about 367 (342 w/ a draenei in your grp and drops to roughly 270 with a balance druid or shadow priest in your grp.) So, to max your DPS, gem for hit (in your yellow sockets) until you can reach your hit cap with just the +hit on the gear. Like stated above, it doesn't matter how much +spell power you have if you're missing all the time.
Personally (after reaching hit cap, of course,) I tend to use a couple yellow sockets for +crit. I like to keep my crit around 30+%. I don't like to stray much higher than that due to threat issues. Once i get my hit and crit where i want it, I'll look for more haste. Haste is nice to have, but not really necessary.
As far as stacking intel... it really depends on your spec. An arcane mage will need more intel, seeing as how arcane builds are more mana hungry. But, if you have mana issues and go oom all the time, you really shouldn't be trying an arcane spec anyway. Back to my main point. even in arcane spec with the +spell power per intel, you're really not getting much dmg from it. My old figures showed 1 int = 0.15 sp dmg (if this is accurate, idk.) So really, the only point to stack intel is for your mana pool.
For gemming, I really just like to put some nice +dmg gems in there, regardless of the slot color. The only time I will gem based on slot color is if the socket bonus is good or if i need to socket for a meta.
Anyways, I hope this information was helpful. I know it's an old post, but I was bored... I'm on Rexxar if you're interested in checking me out.