No big changes other than demonic pact duration and it's new CD. I wouldn't drop points from improved demonic tactics though. While it's no longer needed for DP uptime, it's still quite good DPS talent (80-100 DPS / 1 talent point).
Also every time you use something that increases your SP (blood fury, wild magic potion, whatever trinket you might have), make sure the effect lasts until next application of demonic pact.
I have setup my needtoknow to show internal CD of demonic pact like this:
Choose buff/debuff to time: demonic pact
Bar type: internal cooldown
Internal cooldown settings: cooldown duration 20
Most of this stuff is pretty basic but I get asked some of these things 2-5 times a day in IRC and ingame so here you are.
My spec and glyphs are probably the most optimal choices
Spell priority:
Immolate and corruption on target all the time
CoD if the fight is going to last over a minute
Soul fire if decimation is up
Incinerate if molten core is up
Shadowbolt
I don't use CoA and according to simulationcraft with my gear it's a DPS loss during the last 35% anyway. Put it up if you need to move though.
Optimal playing during the execute phase
This is where you can make the most difference. Demo warlocks spend the first 65% of the fight doing bad dps and the last 35% trying to catch up.
Obviously always save your last demon form for the execute phase.
Try to activate your demon form while you have molten core and 4t10 set bonus on.
Activate immolation with 4t10 set bonus on.
Avoid life tapping during 4t10 bonus thoughout the fight (but keep the glyph up).
Don't spend useless globals on demon charge if you don't have to, make your way to melee range without wasting any cast time during life tap/dot globals.
Remember to keep immolate and corruption up. Immolate does more damage per execute time than soul fire (without molten core) and procs 4t10. Corruption buffs your soul fire making it a DPS gain eventhough the damage itself isn't that great.
Remember to keep imp. shadowbolt debuff on target if you are the only one providing it.
Other small things
Macro demonic empowerment to your other spells so you use it on every cooldown.
Try to make sure your life tap glyph buff and mana last the whole duration of demon form.
Use seed of corruption instead of rain of fire.
Gearing
Get to hit cap, 14% with misery / imp faerie fire (that you should have) and without a draenei in your group.
Any item without hit should contain spirit (except tier pieces and boots. ToC25hc spirit boots are quite good, probably only lose to ICC25hc boots). This is simply because you are there to buff the raid, even if you are going to have to pick up items that are not the best for your personal DPS, they still buff the raid enough through demonic pact to be really good.
Spell damage and spirit are the most important stats bacause of demonic pact. Haste is clearly better than crit if you play with a decent latency.
Best in slot item list can be found at EJ.
Addons I use:
Dotimer for dots
Need to know for buff tracking (life tap, molten core, decimation, 4t10)
Bartender, Grid, Mik's scrolling battletext, Shadowed Unitframes, Omnicc, Omen, Quartz, Ora2, Rangedisplay, Tidyplates + Tidyplates: cleanplates
Best resource for you is http://elitistjerks.com/f80/ , if you want to do good DPS, go to that site and read.