Found this (http://elitistjerks.com/f31/t25842-feral_druid_powershifting_macros_thresholds_mana_m anagement/) today. It looks like a great idea!

Here's the low-down. Use this macro to replace your existing Mangle (Cat) button.
#showtooltip
/run if pwx then local f="Cat Form";f=GetSpellCooldown(f)>0 or UnitMana('player')>pws or not IsUsableSpell(f) or CancelPlayerBuff(f) end
/cast [form] Mangle
/stopmacro [form]
/cast Cat Form The above will powershift you if you are not in the GCD, you have enough mana to shift back into cat form, and you have less than 'pws' energy (defaults to 8).


And use this macro to enable/disable the auto-powershift above...
/run local c=DEFAULT_CHAT_FRAME if pwx then pwx=false c:AddMessage("Powershift disabled",1,1,1) else pwx=true pws=8 c:AddMessage("Powershift enabled, 8 energy threshold",1,1,1)end

You can also change 'Mangle' to Rip, Shred, Bite, Maim, etc. in the first macro if you like. And change the threshold at which the auto-powershift kicks in by changing the '8' to some other number in the 2nd macro.

I plan to create two auto-shift macros. One for mangle (PvE and PvP) and one for Maim (PvP). I'll report back later on the success, etc.

WoW almost becomes rocketscience ... Love to see some films with this in action and some actual numbers.

Has anyone had a chance to use this and did it work well/like you expected? Is the automagical powershifting "ability" persistant through log off?

I've been using it for a while now. No it doesn't persist through log off. You could code it to be on all the time but it would be a pain while soloing since you would run out of mana often. I sometimes run out of mana during long boss fights just from the powershifting, and maybe a brez, and have to turn it off. The example above is only for mangle but I use it for shred and rip also.

There is also an addon that allows easier use of this, though it apparently has some bugs. It's called feralkit.

I use this and it works nicely sometimes, though I find that my actual cycles are sometimes not quite as nice as I'd like them to be. I do more damage with it however, so it's fairly good. I would recommend only using it when you're either with a spriest or have JoW on the boss.