DEMONOLOGY

Demonic Empathy - Removed.
This was an interesting mechanic but ultimately it meant three talent points for a 3% DPS increase only part of the time. Deep Demonology builds such as 0/ 53/ 18 have this, but Demonology gets new toys in Patch 3.1.

Demonic Empowerment - This talent spell now has a unique spell effect and sound.
One of my favorite Demonology talents gets new animation and sound effects! Uh... yay!

Demonic Sacrifice - Removed.
As much as I disliked Demonic Sacrifice, it was situationally handy and was part of old strategies. If you see the new talents, though, I don't think you'll miss it much.

Fel Synergy - Moved to tier 1. No longer increases Intellect, Stamina and damage of your summoned demon.
No more 95k health Voidwalkers? Maybe. But the easy accessibility of this spell greatly increases pet survivability across the board, and should be part of every PvP talent build.

Improved Enslave Demon - Removed.
Nobody took this talent to begin with, and since the effects have been made baseline, this goes the way of the Dodo.

Mana Feed - This talent is now a 1-point talent, down from 3-points. Now is the 21-point talent in Demonology. Now grants 100% mana return to your pet, up from 33/66/100%.
This takes the place of Demonic Sacrifice, and is an excellent investment for one point.

Master Conjuror - Increased from 15/30% up to 150/300%.
Massive boost to the talent! What was once a worthless talent was made more appealing with the great changes to Spellstones and Firestones, but this boost is almost freakishly good. This translates to a 240 haste rating for Spellstones and 196 crit rating for Firestones. That's about a 4.27% crit at Level 80. From one of the skippable talents, Master Conjuror just jumped to one of the best ones.

Molten Core - Moved to Tier 6 Demonology.
Why move it down to Tier 6 without improving it? Hopefully they buff this talent some more.

New Talent: Decimation: When you Shadow Bolt or Incinerate a target that is at or below 35% health, your next Soul Fire cast time is reduced by 30/60% and costs no shard. Lasts 10 sec.
This is just amazing. We will finally see Soul Fire used in raids! This is a change that a lot of Warlocks have been looking for. 2.4 second cast Soul Fires that don't chew up our Soul Shards? It's almost too good to be true. Let's hope it makes it live.

New Talent: Nemesis: Reduces the cooldown of your Demonic Empowerment, Metamorphosis, Soulstone and Fel Domination spells by 10/20/30%.
Wow. This talent just rocks. Needless to say, three points here will be mandatory for all deep Demonology builds. The cooldown reduction to Metamorphosis is a huge DPS boost. Even the Soulstone cooldown is excellent raid utility. Definitely one of the best talents in the Demonology tree.

DESTRUCTION

Aftermath - Redesigned. Increases the periodic damage done by your Immolate by 3/6%, and your Conflagrate has a 50/100% chance to daze the target for 5 sec.
Formerly a moderately useful PvP talent, Aftermath now has a DPS increase component. The change to the daze mechanic is excellent, removing the RNG factor, making it more reliable for PvP. An excellent change that lifts this talent up from mediocrity.

Backlash - Moved up to tier 5, up from tier 7. Now requires Intensity (switched places with Pyroclasm).
Since most Destruction builds pick up Intensity to begin with, making a 3% crit available earlier in the tree is a very good thing.

Cataclysm - Now reduces the mana cost of Destruction spells by 4/7/10%. No longer increases the chance to hit.
Not an altogether amazing change, but the cost reduction is huge in comparison to the original. The lost hit isn't such a big deal as Suppression is easily available in Tier 1 of Affliction.

Conflagrate - Spell now works similar to Swiftmend, consuming an Immolate or Shadowflame effect on the target and dealing damage based on the strength of that effect. Reduced to a single rank.
This should be a good change, allowing Conflagrate to scale better with the Warlock. It's also an incentive for players to use Shadowflame, which should conceivably give better returns.

Improved Immolate - Now increases the damage done by your Immolate by 10/20/30%, rather than just the direct damage.
Straight up buff. Yummy.

Improved Shadow Bolt - Now increases the damage done by your Shadow Bolt spell by 1/2/3/4/5%, and causes your target to be vulnerable to spell damage, increasing spell critical strike chance against that target by 1/2/3/4/5%. Effect lasts 30 sec.
This should be a flat DPS increase accross the board, even helpful to Affliction, which now scales better with crit because of some changes to the tree. This also makes the talent more useful to other builds, which rely on Fire damage.

Improved Soul Leech - Now has a 50/100% chance to proc Replenishment.
One of the earliest announced changes, this should be a good raid utility talent that makes deep Destruction a little bit more desirable.

New Talent: Molten Skin: Reduces all damage taken by 2/4/6%.
Not extremely exciting for PvE, this should at least partially answer some Warlock PvP deficiencies.

Pyroclasm - Redesigned. Now increases your Shadow and Fire spell power by 2/4/6% when you critically hit with Searing Pain or Conflagrate. Lasts 10 sec. Also moved down to tier 7, down from tier 5.
No more RNG stuns. Again, a moderately interesting PvP talent has been reworked to become a pretty good PvE talent, contributing directly to DPS.

Overall, there are some pretty good changes there. Demonology looks amazing, and I can't wait to try out Metamorphosis every two minutes or so. Still, Blizzard has stated that these are incomplete, so there are likely to be new stuff in Patch 3.1. We haven't even seen a glimpse of the new, cool Soul Shard system. Without any tests yet, it's safe to say a lot of these changes will result in a straight up DPS boost. Good times.