Ashwin's range
The first three R Ashwin dismissals showed he has ways to dismiss batsmen even when the pitch isn't too responsive. All three dismissals came in different fashions.
Tamim Iqbal: When the ball is new, Ashwin prefers to go around the stumps to the left-handers. From that angle, he keeps the ball really close to the stumps. Some go straight with the arm and the rest turn away. In addition to that he keeps the midwicket region empty, tempting the batsmen to play against the spin. His variation in pace accentuates the problem for the batsman, for stepping out becomes tougher.
Mominul Haque: Once the ball got old, he went back to over the stumps and this time consumed Mominul with a classical offspinner's dismissal. It was a nicely flighted delivery that pitched on a good-length spot within the stumps and spun sharply to find the outside edge. The trick to play such a ball is to stretch fully forward and smother the spin, if possible. Mominul had a very short stride. Ben Duckett played Ashwin in a similar manner during England's tour of India, and paid the ultimate price.
Mushfiqur Rahim: Mushfiqur stepped out and drove one nicely through the empty cover region. A couple of balls later, he tried the same thing but this time the ball was a little flatter in the air and fell a few inches shorter than expected. The ball also went straight with the arm and found the outside edge of the bat. I remember Ashwin doing the same to Joe Root a couple of times in the last series.
Jadeja and the rough
If there's a fair amount of rough created outside the left-handers' off stump, it's almost impossible to negotiate Ravindra Jadeja for a long period. The problem starts with Jadeja's extra pace in the air and gets complemented with his unrelenting accuracy. In decades gone by, batsmen could kick these deliveries away, but in the era of the DRS, it's not a viable option anymore. Deliberate padding is an option only if the ball has pitched outside leg. Jadeja's speed doesn't allow you to sweep, something Alastair Cook found out, and playing on the back foot is the only way to negotiate him. But that's also full of danger, for some some balls land in the rough and the rest in the area between the scruffy patches. It's almost impossible to gauge and negotiate successfully. Shakib's dismissal was a fine example of this.
Ishant's legcutter
There seems to be a useful addition to Ishant's bowling variations. Once the ball got old and started reversing, he did well to make the ball deviate off the pitch away from the right-handed batsman. While his natural length is a little short for exploiting reverse-swing against the tail-enders, his ability to bowl legcutters will make him more potent against the top-order batsmen.