Back in the day, people laughed at Spirit. If a random weapon or armor dropped and its name ended in "of the Whale" we'd snicker (or maybe cry if it was a blue). Even when Spirit got overhauled in 2.4 we weren't totally sold on it, though truthfully it was a crazy improvement. These days my moonkin hardly ever stops to drink while farming.
The thing is... for a raiding moonkin we're typically too busy chain casting to ever fall out of the five second rule and allow our mana to regen based on the value of our Spirit. Spirit wasn't entirely bad (since Innervate is based off of it and Intensity makes use of it), but we really preferred mp5; stable, reliable, and always regenerating.
Patch 3.0.2 gives us a whole new ballgame with Improved Moonkin Form, which translates 15% of Spirit into spellpower when fully talented. It might not be pretty, but it'll pull its own weight. I have 265 Spirit right now pre-patch when self-buffed with Improved Mark of the Wild. That translates into 39.75 more spellpower, just about equal to the Major Spellpower enchant (or it may be equal, depending on whether or not it's rounded up). It's not game-breakingly powerful, but would I turn it down? Not any more than I'd show up to a raid without my weapon enchanted.
Suddenly seeing Spirit on a piece of gear isn't quite the waste it was. Gear might as well read Int, Stam, and Spellpower instead of Int Stam, and Spirit. (Well, not quite, since the Spirit still gives less bang for the buck as far as item budget goes, but it could actually be desirable in absence of actual spellpower.)
A part of me applauds Blizzard's efforts in making a previously wasted stat more useful, even as I cringe at the thought of stacking more spirit. I have this crazy fear that one day I'm going run into a moonkin wearing "of the Whale" solely so he can get more spellpower, and if I do I'm going to be completely mortified.