A quick run through of Cricinfo's stats database tells you all you need to know...
Career averages
Mat Wkts BBI BowlAv 5/Inn
Overall: 39 213 7/66 24.81 20
In Asia: 26 172 7/66 20.54 18
ROW: 13 41 7/83 42.73 2
Clearly dominant in Asia.
As a comparison, and because his name was mentioned, here's Anderson in England, Asia and elsewhere
Career averages
Mat Wkts BBI BowlAv 5/Inn
Overall: 119 463 7/43 28.28 21
England: 69 296 7/43 25.6 17
Asia: 17 55 5/72 28.29 1
ROW: 33 112 6/42 35.28 3
Surprising that the ROW stat is so high, and that is bought down by averaging 24 in the WI. There is definitely a smaller range in Jimmy's numbers (roughly 10 runs per wicket between in England and ROW) compared to Ashwin in Asia and elsewhere which is at a difference of 22 runs per wicket!
A slightly less quick look at statsguru will paint a vastly different picture.
Ashwin -
Mat Wkts BBI BowlAv 5/Inn
Overall: 39 213 7/66 24.81 20
In Asia: 26 172 7/66 20.54 18
ROW: 13 41 7/83 42.73 2
Anderson in his first 39 matches -
Mat Wkts BBI BowlAv 5/Inn
Overall: 39 134 7/43 34.26 6
England: 24 98 7/43 29.18 5
Asia: 5 12 4/40 45.41 0
ROW: 15 36 5/73 48.11 1
It's vastly disingenuous to compare the stats of one bowler just entering his prime to another whose career is beginning to end. Anderson's overall record in Asia is incredible without a doubt but it took him time and experience to get there. As did McGrath. Dale Steyn was very good in the subcontinent much quicker and that's just one other thing that sets him apart. And typically spinners take longer to mature than pace bowlers. Almost all great spin bowlers started off with average away records. If you can actually look at Ashwin's stats after setting down them chips on your shoulders you will find that they are in fact remarkable.
For those of you who haven't seen Ashwin a lot - I have watched him bowling from the time he was a teenager. When I first heard that he made it to the test team on the basis of his t20 bowling I was surprised. He mostly bowled flat and quick back then. I was even more surprised when he destroyed admittedly mediocre sides at home and effectively ended Harbhajjan's career. But not at all surprised when he failed against Peterson and Cook. I had even predicted India's defeat back then. And sure enough, he struggled and lost his place in the team as he failed horribly when the team toured. But what happened in the next one year or so, behind the scenes, is why so many people are so excited about Ashwin. He unveiled a more conventional action in the limited overs games before the tour to Australia. He still waddled liked a duck to the crease but the finish was totally different. He was more side on, his left arm was fully active and he was really throwing his body behind the ball. Suddenly, he was flighting the ball more, getting drift and dip. He played three matches in Australia that year and didn't get a lot of wickets but you could already see that he was vastly different bowler. This is just a guess on my part but I have a feeling in that one year he must have seen a ton of Graeme Swann's footage and broken down and distilled all the classical offspinner's virtues. He has been refining these virtues tirelessly these last couple of years. He has always got a lot of bounce and that combined with his turn and accuracy makes it very hard to cut him. He frequently bowls with 7-2 fields these days without a point and plugs the leg side completely. He is also landing the natural variation where the ball lands on the non-seam part of the ball and goes straight on frequently. Its nigh on impossible to pick out of the hand or play it off the pitch. He also bowls the arm ball and the carrom ball although he mostly uses these to keep good batsmen on their toes or to run through tailenders. While mastery of the classical off spinner's virtues make him so great what sets him apart is clearly his intellect. It is what allowed him to completely reinvent himself and it is what makes him so dangerous on the field. He is constantly analysing and setting plans. You don't really need stats to see how good he has become. If you had just watched him operate against Kane Williamson these last three innings, that would have sufficed. I'm guessing you will see what the fuss is soon enough. Or not
Will he be much better when he tours England and Australia next time? Almost certainly. Will he be running through sides? Probably not. I'd imagine the odd five wicket haul here and there but mostly he will command respect and tie up one end. And that would vastly improve the way our fast bowlers perform. Thus ends my mini primer on Ashwin.