General summary is that Guile got mostly nerfs and just one buff to his upside down kick. DJ and Hakan only received buffs. Seth got both buffs and nerfs.
Too bad no changes were mentioned for Guile's Shades move. It would have been funny if it was given a boost in some form. We will possibly see a lot of Guile users switching over to DJ. However, it can be argued that certain USA tourney Guile players will stick with him. Note that Lamerboi, Dieminion, Dagger G, Warahk aka wolverine sideburns have stuck with Guile from vanilla SF4. Daigo was the only one that added Guile to his tournament repetoire after realizing how Ryu isn't as strong as he was in SSF4. Daigo and Dieminion are like the only Guile players that have actually won tournies. I think each of them only won one tourney with Guile.
If you hate Seth users before you might hate him more after the AE update. Hakan who was generally thought of as low tier might have a chance of climbing up the tier list.
From Eventhubs
Guile
Unique Attacks
• Deleted hittable box for his Reverse Spin Kick (Toward or Back + Hard Kick) from his knee and below during the first few frames after starting up and reduced its damage. With this adjustment, it's possible to make attacks like Ryu's Crouching Medium Kick whiff and hit them out.
• Spinning Back Knuckle's (Toward + Hard Punch) damage reduced.
Special Moves
• Sonic Boom's meter gain at startup is halved, and we adjusted his meter gaining rate through the match.
• Light Kick, Medium Kick and Hard Kick Flash Kicks damage reduced.
Ultra 2
• Sonic Hurricane's damage has been reduced, and the startup time is a bit slower.
Overall
• Damage nerf is applied to Special Moves and his Ultra 2, so we can say his damage is reduced throughout.
• He will require more attacks to finish off opponents.
• There are almost no changes to his frame data, so in Arcade Edition he can do everything that he can already do.
Seth
Normal Moves
• His Toward Jumping Hard Punch's number of active frames is doubled, so it's easier to hit with now.
• Far Standing Medium Kick's active frames were lengthened a little, and his hittable box when he extends his leg horizontally was reduced, so it will function better as a poking tool.
• Close Standing Medium Punch's startup is faster and the total duration of the move is reduced as a result, plus frame advantage on hit was increased, so it got significantly buffed.
• Crouching Hard Punch's start up is faster.
• Crouching Medium Kick has slightly more active frames.
• Neutral Jumping and Jumping Away Hard Punch (Stretchy Arms) now is his Jump Toward Hard Punch animation. The jumping stretchy arms attack has been removed.
Unique Attacks
• His Dive Kick's hitstun and blockstun were decreased, so it's slightly harder to use the move as an offense tool.
• All three Head Stomp moves had their active frames reduced, and the timing to hit all three of them was changed.
Special Moves
• Sonic Boom's recovery was reduced by 1 frame, and EX Sonic Boom's recovery is reduced by 3 frames. Now regular attacks into his regular or EX Sonic Boom, Focus Attack Dash Cancel and a follow up combo are pretty powerful.
• His Spin Kicks (Hyakuretsukyaku) deal more damage and less stun.
Super Move
• Super's invincibility window was lengthened, and "the pursuit priority is increased." [Translator's note: It's assumed this means it will connect more hits against airborne opponents instead of the attack not fully connecting when someone jumps into it.]
Ultras
• Ultra 2's recovery was shortened.
• Full invincibility was changed to 12 frames, and after that Seth is only invincible to projectiles until the end of active frames. In SSF4, according to the frame data, Seth was invincible for the first 88 frames of animation, so this is a significant reduction.
• Ultra 1 deals more damage, but has a longer recovery time.
Other Stuff
• Stamina increased to 800, stun increased to 900. In SSF4 it was 750 for both his stamina and stun ranking.
Overall
• The changes on SSF4 Arcade Edition happened only where they affect the way he is played.
• He looks weakened in the first glance, but he also got strengthened in various points, so please research his playstyle in SSF4 Arcade Edition.
Dee Jay
Normal Moves
• Far Standing Light Punch's hittable box around his arm was removed, so it's more difficult to beat this attack.
• Crouching Medium Punch's priority was strengthened, and it deals more damage.
• Close Standing Medium Punch's active frames were increased by 1, so it's easier to use as anti air.
• Far Standing Medium Kick was changed to be a 2-hit normal, and it got adjusted in damage distribution, in startup, and in the total duration. Now, the 1st hit is Cancelable, so combos such as Crouching Light Punch, into Far Standing Medium Kick, into Special Moves and also Close Standing Medium Kick into Far Standing Medium Kick into Special Moves combos are possible.
• Close Standing Hard Kick, when it hits airborne opponents, will knock them out in the air, and the 2nd hit of the move has pursuit property.
• Far Standing Hard Kick's startup is 1 frame faster, and the active frames for it was increased by 1.
• Crouching Hard Kick's distance was shortened, but has more active frames, and it will recover faster after the active frames end.
• Toward Jumping Medium Kick's pushback on hit is adjusted, so combos after crossing up with it are easier.
Special Moves
• Air Slasher's (Fireball) recovery got shortened, and the hitstun/blockstun got reduced as well. There are no changes to EX Air Slasher. Opponent's attack will now be registered as a counter hit if you get hit out during the whole move, so if the opponent jumps in on you, you will be in a world of hurt.
• Light Dread Kicks' (Double Rolling Sobat) startup was changed to 12 frames, and his lower body invincibility was lengthened as well. It's comboable from Light attacks now. It's throw invincibility and airborne state were removed.
• Medium, Hard and EX Dread Kicks (Double Rolling Sobat) 1st hit deals longer hitstun, so landing the first 1st hit, Focus Attack Dash Canceling, and following up with a combo may be great.
• Machinegun Upper's damage was increased.
• Light Jacknife Maximum (Up Kicks) damage was increased, and is completely invincible until active frames end.
• Hard Kick and EX Jacknife Maximum hitbox was adjusted in order to prevent it from whiffing some hits after connecting it.
Ultra 2
• Ultra 2's recovery time was reduced as much as possible.
Other Stuff
• Dee Jay's forward dash has more frames where you can input a Super or Ultra command. As a result, his forward dash into Ultra 2 is easier than it was before.
Hakan
Normals
st.HP's hurtbox around his arm got smaller, so it's easier to use as an AA or a poke.
When Oiled, even when normals are input during forward dash he will still slide a little. (Translation incomplete.)
Unique Attacks
Step Low (F+LK) got to be cancelable.
Specials
For Oil Shower, the duration of the oil will be stacked now. The maximum duration will be 30 seconds.
Also, MK/HK/EX versions have 5f less recovery, and EX version can be canceled into Guard Position (D+3P, aka coward crouch).
Also, Oil Shower will be one of the follow-ups after Oil Slide.
The effect is the same as LK Oil Shower, and he will be in advantage nevertheless.
LP Oil Slide has faster start-up, and can be connected from cr.LP or Step Low.
Oil Dive (including EX), while holding button, can be canceled into Guard Position.
Others
Oil Rocket, Oil Dive's input property is adjusted, so the feeling will be same with that of Zangief's SPD.
