Thus begins my long process of typing random stuff about rogues.     If there's something in particular you wanna see first, post it.   Otherwise it'll be a random thought.     To start off with:

 Sources:

• WotLK Pocket Guide
• Roguecraft Spreadsheet
• Optimal Mutilate Spreadsheet

Quick and Dirty FAQ:

1.  What hit rating should I be at?

• STFU about hit rating.   First off, there is no magic number.    Second, caps are only around so you're aware how they affect the relative value hit rating.    AP, Agi, ArP, Haste, Crit, Exp all give you dps too in some degree.   All you should want to know is how much each is worth, not specifically aiming for any magic number for any of it. 
• There is one possible exception for Mutilate rogues, being Expertise capped (and yellow hit capped) is usually very worth it.   Your cycles are highly dependent on Envenom hitting, and the stat weights generally reflect this value anyways.
• Use one of the spreadsheets

2.  I heard fast daggers were good for mutilate, should I use 2 fast daggers?

• Speed is just another stat.   Slow daggers work fine if they are sufficiently above in quality over fast daggers you can obtain.

Upcoming Changes in 3.1:

General

• All classes now receive 25% more benefit from Armor Penetration Rating.
• Applying a glyph no longer requires a Lexicon of Power. The same rules for switching between dual talent specializations now apply to switching glyphs and cannot be performed while in combat, Battlegrounds (except when Preparation is up), or Arenas (no exceptions).

Skills

• Envenom now gives an additional 15% chance to apply Deadly Poison and a 75% increased frequency of applying Instant Poison for 1 sec plus an additional 1 sec per combo point. (Previously gave a 15% chance to apply both deadly and instant poison) 
• Expose Armor now reduces armor by 20%, lasting longer per combo point.
• Shiv: This ability can no longer generate a critical strike, and the poisons it applies cannot be critical strikes either.
• Deadly Throw: Missile speed increased.
• Master of Subtlety: The amount of time remaining on the damage bonus for this talent is now displayed.

Assassination

• Hunger For Blood (Tier 11) changed to: Enrages you, increasing all damage caused by 15%. Requires a bleed effect to be active on the target. Lasts 30 sec. (Previously increased damage by 5%)
• Hunger for Blood now lasts 1 min. Energy cost reduced from 30 to 15.
• Improved Poisons (Tier 4) changed to increases the chance to apply Deadly Poison to your target by 2/4/6/8/10% and the frequency of applying Instant Poison to your target by 10/20/30/40/50%. (Previously increased chance to apply Deadly and Instant poison by 2/4/6/8/10%)
• Master Poisoner: Now also increases the bonus to apply Deadly Poison when Envenom is used by an additional 15/30/45%.
• Lethality now affects all combo point-generating abilities.

Combat

• Savage Combat (Tier 9) now increases damage caused against poison enemies by 4%. (Previously increased damage by 1%)
• Adrenaline Rush (Tier 7) cooldown reduced from 5 minutes to 3 minutes.
• Killing Spree: Now also increases all damage done by the Rogue while active by 20%.
• Lightning Reflexes (Tier 4) is now a 3 point talent and Increases your Dodge chance by 2/4/6% and gives you 4/7/10% melee haste. (Previously just increased dodge by 1/2/3/4/5%)

Subtlety

• Sinister Calling now increases your total Agility by 15% and increases the percentage damage bonus of Backstab and Hemorrhage by an additional 2/4/6/8/10%. (Up from 1/2/3/4/5%)

Glyphs

• Glyph of Sap  -- Increases the duration of Sap by 20 sec. (Old: 10 sec.)
• Glyph of Deadly Throw  -- Increases the slowing effect on Deadly Throw by 10%. (Old: Increases the range on Deadly Throw by 5 yards.)
• Glyph of Adrenaline Rush  -- Increases the duration of Adrenaline Rush by 5 sec. (Old: Decreases the cooldown of Adrenaline Rush by 60 sec.)
• Glyph of Sprint  -- Increases the movement speed of your Sprint ability by an additional 30%. (Old: also reduced the duration by 5%)
• Glyph of Crippling Poison  -- Increases the chance to inflict your target with Crippling Poison by an additional 20%. (Old: 10%)
• Glyph of Pick Lock -- Reduces the cast time of your Pick Lock ability by 100%. (Old: 75)
• Glyph of Hunger For Blood *new*  -- Increases the bonus damage from Hunger For Blood by 3%
• Glyph of Killing Spree *new*  -- Reduces the cooldown on Killing Spree by 45 sec.
• Glyph of Shadow Dance *new*  -- Increases the duration of Shadow Dance by 4 sec.
• Glyph of Fan of Knives *new*  -- Increases the damage done by Fan of Knives by 20%
• Glyph of Tricks of the Trade *new*  -- Your Tricks of the Trade grants an additional 10% bonus damage to your target.
• Glyph of Mutilate *new*  -- Reduces the cost of Mutilate by 5 energy.
• Glyph of Cloak of Shadows *new*  -- While Cloak of Shadows is active, you take 40% less physical damage.
• Glyph of Backstab - Each time you Backstab, the duration of your Rupture on the target is extended 2 sec, up to a maximum of 6 sec. (Old - Increases the damage dealt by Backstab to stunned and incapacitated targets by 20%.)

Early Testing on PTR:

• Instant Poison - PPM appears to be between 7.99 and 9.16 if PPM is reduced by haste, if not, it could be between 7.43 and 8.52 PPM.
• Wound Poison - 21.27 - 21.76 PPM
• PPM believed to be normalized to 1.4 speed at current proc rate (i.e. WP is 50% with a 1.4 spd weapon), so slower weapons will get more poison procs than current.
• Deadly Poison - is not on the PPM, coefficient raised to 0.12*AP
• It appears Lightning Reflexes is not worth it for Mutilates, so traditional build still
• With the new Master Poisoner, fast OH still beats slow, so SR / WD is currently slated to be best to enter Ulduar with