Several days ago I decided to swap my gear optimization from crit fire to haste frost. As part of this I downloaded and ran Simcraft.
Surprisingly, Simcraft weighted int at something like 5.27 and haste at around 2.50. Based on those results 1 point of int was worth more than 2 points of haste. At the time I got these results I had gemmed for max haste.
Based on those results, I then swapped my gems from pure haste to int/haste. This raised my int but lowered my haste.
I then ran Simcraft again... and got the opposite result. Now that my haste was lower, haste was worth more than before. 1 point of int was no longer worth more than 2 points of haste.
It looks like that optimum result for me, at least according to Simcraft, would be to have some pure haste gems and some int-haste gems. I didn't want to spend thousands of gold trying random combos and guessing though, so for now I'll just leave most of my gear int/haste.