Straight haste is a bad call. If you can't reach the cap, then haste isn't that great - it's Fantastic if your getting to the 8085 haste breakpoint, but prior and after that it's only marginally better than mastery or crit. Int is by far our best stat, I highly recommend gemming for socket bonuses - using int and int/haste and int/spirit (if you need hit) gems.
Also, not sure if your using it or not - but get HaloPro, simple addon that lets you snipe Halo to Exactly 25 yards - which is critical for an ability that deals a good bit less damage if its 24 or 26 yards (or worse). Precision with our 90 talents is key to MoP Shadow - HaloPro is, imo, mandatory.
(or, at least for Halo).