Sure the penalty is fair. If 120 spellpower has the same effect on throughput as 120 haste (hypothetically), you would take the spell power because of the free regen tagging along. It would be 120 SP = 120 Haste + x Mp5. Where x is maybe around 15. Now if you do not value Mp5 at all, meaning that you set your stat weights for mp5 to 0, then yes, you would be indifferent between 120 SP and 120 haste. (There is a small difference between the two. You would probably prefer SP in 10 mans, and haste in 25 due to the number of available targets) Therefore Haste takes a penalty that is proportional to how much you value regen.

If you really don't value regen, you would be gemmed straight spellpower/haste with the spell power meta gem. You would also be wearing as much haste/crit gear as you could (since crit > spirit > mp5 = 0), and Illustration of the Dragon Soul would be BiS trinket. You would avoid Mp5 as if it were hit.

If you respond to this with: I need the Mp5 I currently have, but why would I want any more? then I could respond the exact same way about spell power, or throughput in general. More regen allows you to cast spells you wouldn't be able to if you needed to manage your mana. More haste (if used) does lower regen, effectively taking away from your current Mp5.

EDIT: If Regrowth becomes the new heal of choice for raid healing, then mana will probably become more of an issue than it is now.

2T10 isn't too hot - 3% increase to WG - but it's better than no bonus and you get it by using haste pieces so we'll probably end up having it, at least until the heroic gear starts flowing.
As for the crit, as I wrote this was obviously gonna happen, our gear was plagued with crit since WotLK launch. Nothing before 4.0 is gonna fix that. Hopefully every slot will have a haste piece, this isn't short ToC after all.
Maybe the total lack of spirit on DPS caster loot will finally stop them from taking spirit for Molten Armor or whatever other minuscule bonus it grants. Haven't seen any posts about them doing it before Cataclysm though.

All of our sets have been 3/5 crit and 2/5 haste if I remember correctly so there is little deviation here. Not to mention we have hardly been plagued with crit on our gear at all in this expansion but we have had almost no use for what has been on it fair enough.

This also excludes the ability to work around some of the frustrating crit items with the cloth versions that we have done in the past.

Not sure what you mean by "this". Should be plenty of leather and cloth gear with haste in a large raid as ICC.

The theorycrafting numbers I've seen on this forum over the past month or so seem to match a point of spell power to a point of haste pretty well, in which case a +23 SP gem slightly beats out a +20 haste gem for throughput. So, I'd stick with +23 SP gems where practical, and use SP/haste gems in any yellow slots.

I'm going to go out on a limb here and say that despite the theorycrafting you could reasonably choose to gem haste over spellpower up to the cap anyhow... I'm sure to disturb some here who prefer to "math it out" on all occasions and generally I'd agree with them if we were discussing dps or tanking. Healing isn't quite as one-sided however.

Basically I would describe it as a choice between "spread" and "focus", with haste being spread friendly and spellpower being focus friendly. Favoring haste allows you to heal slightly more different targets for slightly less - good for a raid healer, which is the role we typically assume already.

If the stats were farther apart in the theorycrafted values I would also disregard the "fuzzy logic" above, but the fact that haste is performing decently even in theory settles it for me. Simply because faster casts have such a strategic value for a healer, giving more choice and flexibility. If we find ourselves wanting to increase focus, i.e. heal fewer targets for more, we have and always have had the option of layering multiple hots and following up with direct heals.

Raid composition and healer teamwork in your particular group could also affect this question - if you usually have clear assignments (e.g. "Flowerdrude focus on groups 2-3") then haste may appeal less to you.

Haste performs comparably or slightly better than spellpower in terms of raw healing (will have to check spreadsheet).

I think you can make a good case for gemming haste, in that it enables to you choose between focused or spread healing by swapping Rapid Rejuv in or out. When you want to be spread, you won't use the Glyph, and haste is better than spellpower (both higher overall healing and better spreading). And when you want to be focused, just swap in the Glyph, and now the haste adds just as much HPS to your ticking Rejuvs as spellpower would.

The glyph speeds up the ticks of the rejuvenation, lowering the total duration of the rejuvenation since the number of ticks remains constant. Instead of lasting say 17 seconds, it would last something like 13 seconds. That means if you are hotting on CD every second, you can only have 13 rejuvenations up instead of 17 which means you're covering less the raid.

Most people agree that the hasted hot is not optimal for raid healing where the majority of our hots are overhealing. You want as many rejuvs up as possible for when the raid damage does hit.

Where I'm seeing the difference it focus v. spread is in raid comp. If I'm the only druid raid healing and blanketing rejuvs on as many as possible, I'd opt out of the glyph. With other druids, have a smaller focus of groups for each, and use the glyph.

Although, I guess I'm looking at the reverse of Thorngrip, and thinking of haste for focus, and sp for spread.

At any rate, my expectation (untested at this point, as haven't had 25-man experience on the ptr, only 10 - and obviously 10 is focused already), is to meet the cap and switch out the glyph.. thus will have to be gemming a bit of pure haste up-front with my current gear.

You don't want the glyph for spread, as when we are raid healing we want to get the most healing we can on the most people in the raid, i.e. 17 people rejuv blanketed (assuming full Nature's Splendor). You don't want to make your rejuvs hit faster on a non-tank raid member, which is what the glyph does. Just in case some of you are confused on the actual mechanics of the glyph it DOES NOT make your rejuvs hit more times within the 17 seconds, it instead reduces the time in-between the hits, lowering the overall time that the heal last on the target. All this is looking at raid healing a 25 man by the way. If we look at the 10 man version the glyph might very well be viable as the duration for rejuv will still be over 10 seconds even with the glyph/haste capped, allowing you to still completely blanket the raid and have faster healing, giving a nice meter padding.

Even in 10 man it is somewhat annoying using the glyph unless you are assigned to cover a Felmyst-esk aura (and need the glyph in order to manage it) as it really hinders your ability to blanket the raid and then play reactively especially if you only use 2 healers as standard. Meter padding is wonderful I know but if you don't actually need the healing it provides then it (to me) becomes more of a hindrance than anything else.

If you take the route of having tight assignments (3 healers in 10, and 1-2 groups on 25) then it will become more useful but if that is not the case and you also don't need the increased healing it provides specifically then the people who just take the glyph for the sake of it upon 3.3 will no doubt find themselves worse off more often than not.