There seems to be a lot of misconceptions about how good spirit actually is. I'm not going to advocate stacking spirit in any way, aside from putting in Purified gems in blue sockets to get decent bonuses, but to say it's a bad stat, or one that should be avoided on gear is going too far imo. Obviously if your choices are like the frost badge gear where you can get a piece loaded with spirit or one with haste instead, then haste is the way to go, but not all your gear choices are that easy.
I'm a bit picky about knowing my stat weights, so I run simcraft every time I upgrade my gear, and in my current gear (4 piece t10 with mostly 251 gear) spirit is almost as good as crit. My current weightings look like this:
SP: 1.95 Haste: 1.87
Crit: 1.37 Spirit: 1.15
Int: 0.4
So comparing
http://www.wowhead.com/?item=50807 with
http://www.wowhead.com/?item=50392 the tier piece obviously has better itemization, with the tradeoff being 10 SP and 88 spirit on the non-set piece for 96 crit on the tier piece. With my current stats, the better itemized tier piece still wins, but only by about 11 dps (that's about a 1.6% difference).
So essentially I'm not trying to negate anyone's previous advice here, keep taking green stats over spirit, but what I'm trying to say is not to group spirit with int in terms of dps increase. Don't pass on spirit gear just because it has spirit, do your homework on upgrades before the gear even drops.