One of the few classes I haven't played very much is Boomkin (also sometimes known as Oomkin and even more rarely as Moonkin). I had to remedy that situation of course, so I respecced my 80 druid boomkin and also rerolled a little boomkin alt on another server. I usually think you need to do something properly to actually know something about it, and doing a class properly means leveling as one.
One of the first issues when becoming a boomkin is of course, what talents should I choose? My usual solution is to check out the talents of boomkins all around me. But this quickly turned out to be problematic, as they hadn't specced alike. And I figure that some talents might be better for heroics and some be better for raids. But then I noticed some had specced Dreamstate and some had specced Intensity (in the resto tree). So I thought I had to find out which one is better.
Fully talented they do the following;
Intensity - Allows 50% of your Mana regeneration to continue while casting and causes your Enrage ability to instantly generate 10 rage.
Dreamstate - Regenerate mana equal to 10% of your Intellect every 5 sec, even while casting.
The following calculations are based on being fully talented into either talent for simplicity, although it is more common that one takes one or two into either.
First of all, Intensity and Dreamstate are affected by two different stats. Intensity is indirectly affected by spirit and Dreamstate is directly affected by intellect. I say indirectly since spirit gives "Mana regeneration" (intellect does affect this too however). According to wowwiki a thumbrule is that 1 spirit approximately (very roughly though) gives 1 mp5. That means 50% of your spirit will turn into mp5 while casting with intensity.
Just looking at it one would say that 50% of something does sound alot better than 10% of something. But we of course have to look at how big that "something" is in a boomkin. Considering Boomkins want alot of intellect anyway for +crit (which is good for Moonkin Form and Eclipse), the Lunar Guidance talent, and big manapools most boomkins actually run around with alot of intellect. But five times more than spirit? Let's see.
The best place to start looking is the boomkin tier 10 set, since that would be itemized with exactly the stats that Blizzard think a good boomkin should collect (this could be discussed however, it is widely known that Blizzard and number crunchers don't always agree). When looking at that set we quickly see that it holds no spirit. Zero, zip, nada. It does however hold a bunchload of intellect. Does this mean boomkins don't get any spirit in their gear? Hah, if only (I can hear some boomkins say). "Unfortunately" boomkins have to share alot of their gear with resto druids which usually has alot of spirit on it, which of course means in the end even boomkins get some amounts of spirit. As I wrote some months ago however, boomkins do tend to avoid spirit gear, because spirit doesn't actually bring anything for a boomkin (unless they spec Intensity). They even avoid it so much they look longingly at the way better itemized cloth gear and claim those items to be Best in Slot. Back then one of my theories was that they didn't want leather gear because it had spirit. Even resto druids happen to avoid spirit gear. Spirit has simply, after a alot of nerfing from Blizzard, turned into a not so good stat. Not for any class. And certainly not for a boomkin. EDIT: Well that's not completely true. With improved moonkin form, boomkins actually get 30% of their spirit turned into spellpower. Yet most boomkin gear has no spirit? So it seems that even with a talent like this boomkins are supposed to avoid spirit, and simply have some benefit from the spirit they no doubt will acquire.
But, since boomkins now do get spirit in their gear, whether they like it or not, they might as well take the bull by the horns and grab intensity, right? Well maybe. If you happen to have alot of spirit gear on you right now, it might be the wizer course of action. As long as you have less than three times the amount of intellect over spirit, Intensity might be the better choice. But speccing to use a stat that you're trying to avoid doesn't seem like a great solution in the long run. Boomkins do want alot of intellect and that means you should make that stat as profitable as possible. Unless you happen to be a resto druid just hobbying as boomkin (like me for the moment) I recommend against talenting Intensity and definitely go for Dreamstate. But best solution would be to keep an eye out and switch between these two to whichever is best with your current gear.
EDIT: Something I didn't think about at first, but as a raiding boomkin you'd also want to take replenish into consideration, which is based on manapool (aka intellect). The bigger the mana pool the better the replenish = the more intellect the more regen. But that's just a sidenote as that doesn't affect the talents. It just makes Intellect an even better stat.