This goes for all casters too, and its relatively straight forward.
TLDR: Int > Hit > Everything else, spec dependant. You still want the hit cap, but you need to get there by gearing, not by gemming. If you can't reach the cap even with reforging, go get better gear.
Hit is the best of the "Rating" stats. You still want it, you still want to cap it, but you no longer want to gem it. Intellect is the best stat you have and all efforts should be made to get as much of it as possible regardless of your capability to hit the Hit Rating Cap. When you have exhausted all other options for getting more Intellect, you then focus on your Hit Rating at the exclusion of all other "Rating" stats.
I want to make sure you guys understand - this is not a comparison between sub-10% hit rating and hit cap. That's just stupid and exaggerated. This is a comparison between gemming Intellect vs Hit Rating when you are not at the hit cap. In other words, this is a comparsion between X% Hit and X+2% Hit, or however much extra hit you might get from the gems. Making this gap any larger just shows you have no concept of how gearing works and should really not post in this thread.
The reason for change in Cataclysim is rating conversion and itemization, not because some program worked it out and thinks its good. It's not because some yahoo who moderates a forum thought out that if has a fight where he never missed then hit rating was worthless. There is a reason, and here it is.
Lets start with a basic assumption: I think we can all agree that reducing your chance to miss by 1% results in an approximate 1% dps increase. Yes, I'm aware that there are numbers after the decimal place, but for simplicity's sake lets just say 1% is close enough. (There are people who can prove that 1% Hit is sometimes 1.2% DPS. The following conclusions are still correct in this case.)
At level 70, Blizzard created gear with the following rule: 1 Int = 1 Hit = 1.17 Spell Power
It took just under 15 Hit Rating to get 1% Hit.
15 Int OR 17.55 Spell Power did not result in a 1% dps increase. It was closer to 30 Spell Power to get 1% dps.
Therefore, at level 70, Hit Rating was a better stat because it increased your dps more than any other stat, point for point.
At level 80 (Patch 4.0.1), Blizzard created gear with the following rule: 1 Int = 1 Hit, and made 1 Int grant 1 Spell Power
It took just over 26 Hit Rating to get 1% Hit.
26 Int did not result in a 1% dps increase. (It was closer to 60 Int)
Therefore, at level 80, Hit Rating was a better stat because it increased your dps more than any other stat, point for point.
At level 85, Blizzard created gear with the following rule: 1 Int = 1 Hit, and has 1 Int granting 1 Spell Power
It takes just over 102 Hit Rating to get 1% Hit.
102 Intellect does result in more than a 1% dps increase (70 Intellect grants around 1% dps, 102 intellect is around 1.45% dps)
Therefore, at level 85, INTELLECT is a better stat.
To explain further, even with base damage increases, spell coefficients did not change so drastically as to complete revamp the way we play. Intellect is still being given to us at a 1:1 ratio and it still scales just as good as it did in WOTLK. However, Hit Rating is now being given to us at a 1/4th its WOTLK value, which also reduces its dps value by 1/4th. This is enough to drop it below Intellect.
For you Shamans or other classes saying "This doesn't apply to me because of <spell name vomit>" - the only way this doesn't apply to you is if Hit Rating was valued at 4x Spell Power in WOTLK. I.E. Warlocks had 2.0 dps per Spell Power, so for Hit to be better than Intellect it would have to be 8 dps per point of Hit rating (it wasn't, it was 3.5). I have yet to see any proof that Hit was valued so highly so please post it including links to 3.3.5 Scale Factors before you claim otherwise.
This is how I would gear, in a semi-real life example
1) I got 333 in every slot and started collecting 346's and getting BOE/Rep epics.
2) I looked at what I had and realized I could only hit 15.5% Hit Rating - I still gemmed Intellect.
3) I went out and farmed 3 instances that drop a side grade to replace a Crit/Mastery item with Hit/Crit.
4) I reforged and hit 17.2% Hit Rating - I still gemmed Intellect.
A few things:
1) If I were a Shaman who might be asked to interrupt, then obviously maximum dps is no longer my primary concern and I would hit the cap at the expense of my dps. As Andromalia said, this is a MAX DPS discussion, not a raid survival discussion.
2) Hit cap is more important that Haste, Crit, and Mastery Rating, but since I just didn't have enough of it due to luck with drops, I was under cap and still gemmed intellect.
3) If I had a fight where I missed with any spec-defining ability w/ a cooldown, such as Conflagrate, Haunt, Lava Burst, Mind Blast, Hand of Gul'dan, Deep Freeze, Flame Shock, etc, I would chalk that up as a bump in the road on my way to getting proper gear.
There are lots of people who are saying "Gem and enchant for hit until capped, its the best dps stat" and they are wrong. Intellect is the best dps stat as I have shown you. Sometimes missing will cause your dps to go down, and the amount is dependant on what misses. I get it, you do not need to post it over and over and over again. If you choose to get hit capped at the expense of intellect, you are trading sometimes higher dps and rarely lower dps for consistently average dps. The difference is under or around 500 dps, and is not so significant that you will be called a terrible player. It's personal choice. All I ask is that you stop regurgitating "HIT IS DA BEST U MUST BE DUM" all over the damn place - this proves that you are terrible rather than just having a personal preference.
PS: Try to get runspeed to boots instead of Hit Rating, as the healer mana/attention gains it potentially provides far outweighs any dps discussion.