Just to play devil's advocate here, statistically Tiger isn't that great of a putter at all.
Look at his Masters putting stats:
The Official Site of the Masters Tournament
46th of 50 who made the cut. If he had putted as well as the average at the Masters, he would have won it.
He's only ranked so-so in putting in the critical 10-15' range (159th in 2008, 144th in 2009 going into the week).
And I don't completely buy the "clutch putting" idea, either, because in a golf tournament every single stroke is equal. The putts he made on Thursday count as much as the putts on Sunday. I think that he'd given a lot of credit for being "clutch" because he wins a lot, when I think it is his approach shots that really make the difference. He usually leads in at least 1 of the approach categories (distance from the hole from 100-150, 150-200, 200+ etc.) and is near the top in all of them.
Here's quote from putting instructor Geoff Mangum recently "In the recent Masters, Steve Flesch, Sany Lyle, Aaron Baddeley and many many others putted MUCH better than Tiger. Flesch took 14 fewer putts than Tiger, even though Tiger took 14 fewer full swings, and these two tied for 6th. If Flesch had outputted Tiger by ONLY 10 strokes, Tiger would have been in the playoff. If Tiger had putted HALF as well as Flesch, Tiger would have beaten the entire field by 3 strokes. If Tiger had putted the same as the field AVERAGE, he would have won the Masters by 2 shots. These bad putts were all "clutch" in every sense of the word, so Tiger LOST. He has an "L" to show for his lack of excellent putting. That's just the fact, and Tiger knows it and says it. He lost the Masters to OTHER GOLFERS who all putted better than he did. He's done that many times in his career, when a person with more consistent skills would not. So he has some room for improvement -- a lot. "
Objectively, he just isn't that good of a putter all around. He's given credit for putting because he keeps winning, but there is definitely room for improvement.