Players and manufacturers suggest the USGA/R&A 2010 groove rule changes have had minimal impact, but Mike Stachura parses some stats and finds there is strong evidence of the rule change successful combating ball control from the rough.
Mind you, the whole driving accuracy=money won thing has never been a very good justification for the rule, but the grooves aiding those hitting shots out of less than perfect lies has been a strong justification for the rule.
From this week's Golf World:
Shotlink research also reveals a peculiar development for approach shots hit from the rough. It seems the tendency to hit shots well past the hole, like you would see from the so-called flyer lie, has dramatically increased in the years following the implementation of the groove rule. A recent study shows that the number of shots that end up 10 yards or more past the hole has increased 37 percent compared to pre-groove rule years. The number of shots PGA Tour players hit from the rough that end up past the hole by 10 or more yards is, of course, a fairly small number, but the change in that trend could be viewed as more than coincidental.