We'll choose between these:

Chain Lightning - Strikes 2 additional targets, deals 10% less initial damage
- PvE

Elemental Mastery - While active, take 20% less damage
- PvP

Fire Nova - Increases radius by 5 yards
- Both

Hex - Reduces cooldown by 15s
- PvP

Lightning Shield - Can no longer lose charges to attackers when at 3 or less
- Awesome for leveling (due to the new talents), not for raiding.

Shocking - GCD of Shock spells reduced to 1s
- Both

So seems like there's some choices to be made.

Are you kidding? I had a hard time narrowing it down to 3! And I'm talking PVE here, too!

* Chain Lightning - Strikes 2 additional targets, deals 10% less initial damage. Potentially useful, though probably not practical.

* Elemental Mastery - While active, take 20% less damage - Your healers will love you, first of all. Not to mention, a dead DPS does 0 DPS. This gives us a PVE defensive cooldown. We sorely needed it. Think Festergut if you miss a spore. Almost every other class has a trick they can use during it to save them. Now we do too. Sure, you don't get to use it at the time you wanted, but it will save you more than a few times. Of that I can be sure.

* Ghost Wolf - Additional 10% movement speed. Ghost Wolf is indoors now, so this is 50% movement speed. Perfect for "I have the big explody debuff and I need to get out of the raid" situations.

* Healing Stream Totem - Increases Fire, Frost, Nature resistance - This will be pretty sweet unless it doesn't stack with Mark of the Wild. Almost all buffs were consolidated in Cataclysm, so I wouldn't be surprised if this one was too. But it is nice to have a 4-in-1 totem.

* Hex - Reduces cooldown by 15s. CC is supposed to be a bigger factor in Cataclysm, and making the cooldown on Hex 30s instead of 45 could mean the difference between waiting between pulls and actually killing some more stuff.

* Lightning Shield - Can no longer lose charges to attackers when at 3 or less. I think this one is a quality-of-life thing. If some boss mechanic triggers our shield (which a lot of boss mechanics currently do) and it falls off, we lose DPS refreshing it all the time. This solves that problem.

* Shocking - GCD of Shock spells reduced to 1s. Speculation said that this would be useful even in WotLK. It just makes it so there's one second between Shocking and doing something else, rather than 1.5 (without haste, of course). Considering that Shocks are going to be a larger part of our rotation, this could be a huge time-saver. 0.5 seconds adds up when you think about using one shock every ~9 seconds in PVE. On a 5-minute fight, this saves you about 16 seconds, which is at least 8 more lightning bolts you could be tossing out. That's actually pretty significant in the long run.

* Thunder - Reduces Thunderstorm cooldown by 10s. This is obviously a much better PVP skill than PVE, but honestly, we all use thunderstorm more often than we think to regen mana. Especially in a 5-man run when you don't have Replenishment and you're using Chain Lightning much more often. Time will tell whether our mana actually becomes an issue, but for now, this isn't half-bad.

I'd go with Elemental Mastery to have a defensive cooldown, Lightning Shield (though I'm skeptical of its potential uses), and either Ghost Wolf or Thunder. I'll let the math nerds calculate whether Shocking is a bigger DPS increase than refreshing Lightning Shield things or if mana will be an issue or not. It may end up being EM, LS, and Shocking.

Lightning sheild glyph might be useful especially when combined with Fulmination Talent. Not losing charges once at 3 or fewer would mean you can acheive fulmination faster.

Quoting Squeek:
"* Shocking - GCD of Shock spells reduced to 1s. Speculation said that this would be useful even in WotLK. It just makes it so there's one second between Shocking and doing something else, rather than 1.5 (without haste, of course). Considering that Shocks are going to be a larger part of our rotation, this could be a huge time-saver. 0.5 seconds adds up when you think about using one shock every ~9 seconds in PVE. On a 5-minute fight, this saves you about 16 seconds, which is at least 8 more lightning bolts you could be tossing out. That's actually pretty significant in the long run."

While this is true initially or whilst leveling, once you're at the right haste levels, you GCD for all spells will naturally drop to the 1s minimum, completely devaluing this glyph.
The new glyphs and glyph system on the whole looks really good so far though :D