I can tell you a few changes I have noticed. This is PC version.
Matthews Feint:
Basically, all you need to do is have the ball at your feet in a stationary position, then press first left and then right, or vice versa (where left and right refers to 90 degrees from the direction your player is facing). As you might have guessed, this can be done in both directions by all players it seems.
Drawback Side Extension:
An elaboration of the drawback move. First stand still with the ball right in front of you. Next, hold R2 and press in the opposite direction from where you are facing. When executed, immediately release R2 and press 45 degrees forward in the direction of your players preferred foot. This will make your player first draw back the ball with his sole, and then immediately angle it firward and to the side. Seems quite useful actually. As described above, this move only seems to work torwards the side of your players good foot. Not sure if Weak Foot Accuracy or Frequency matters, or Technique or Dribble Accuracy.
[Stationary Stepover to Dash:
New move where you stand still with the ball close to you (important). Next, tap R2 twice for a quick stepover with the players preferred foot. Next, as soon as you have pressed R2, move the stick 45 degrees from where you are facing, and in the direction of the players preferred foot. If your player is rightfooted, move the stick 45 degrees to the right.
R2 Sprint modified:
Where holding R2 in PES5 meant the player would be running at a pace somewhere inbetween dashing with R1 and just dribbling as normal speed, now holding R2 makes your player dribble the ball slowly with the ball very close to his body. Perfect for drawing an opponent near and then advancing quickly and going past him. Note that only the Two-Foot Feint works from this dribble mode, I haven't been able to perform the drop shoulder when R2-Sprinting. The Two-Foot feint should work great though as the player quickly accelerates when performing it.
Other Noted Changes:
[Drawback Turnaround removed:
It is no longer possible to perform the Drawback Turnaround move that was available in PES5, where you first use the drawback feint (R2 + Back), then release R2, and hold 135 degrees from where you are facing (meaning you hold back and to the side). This would cause the player to first drawback the ball, stop it, and then turn around on the spot and start moving 135 degrees from where you were facing.
Drop Shoulder move made easier
Performing the drop shoulder move now seems alot easier. The window of opportunity for performing the move has increased which means you no longer need split-second reactions and timing to perform it.
For those who do not know, the drop shoulder is generally performed, when running from left to right, by first letting the player kick the ball once, then as he is approaching the ball again, pressing down (in this case, 90 degrees to the right of player movement), and then moving the stick back to the direction of movement at the right time, just before the player kicks the ball forward again. The key is moving the stick back at the right time, the first stick move to the side can be timed very liberally, seemingly at any point after the players kicks the ball ahead.
[R1 + L1 Tapout modified
Holding L1 and R1 simultaneously in PES5 would make the player push the ball out from his body with the outside of his boot. But it wasn't as useful as it could have been then. Now in PES6, the player not only pushes the ball a bit further, but also takes a step back and leans his body forward, and starts running to the ball. This animation sets up nicely for a shot that can pack a lot of punch, unlike PES5 where the R1 + L1 Tapout still had your player entirely stationary, making it hard to pickup any speed when running to kick the ball.
Any more I can think of and I will post.
Also, note that I do not have any info as to how very high "Dribble Acc", "Technique" or "Weak Foot Acc/Frequency" impacts the use of certain tricks. It is possible that skilled and two-footed players can perform some of them in both directions where as it generally seems some are only performable in the direction of the players preferred foot.