I read another forum where people were saying this would allow teams to go for it on 4th and 15 a lot more than they go for it now on the onside kickoff, but I don't agree with this. Even if the odds of converting a 4th and 15th were greater than converting an onside kick, the higher risk of not converting would offset the differences. Here is what I mean: If a team goes for it on 4th and 15, they're likely not going to risk throwing it shorter than 15 yards, so if they don't convert it, it will be because of an incomplete pass, giving the opposing team the ball on the 30 yard line, which is already in field goal range. A team kicking an onside kick from the 35 needs to go 10 yards before they can touch it, but it usually goes a few yards beyond that, and onside kicks (successful or not) are usually not returned for any yards--so if the team fails to convert an onside kick, the opposing team usually gets the ball on the 50 yard line, which is not field goal range for any kicker.
So, because of the higher risk of not converting a 4th and 15 from the 30, teams would only go for it when they really needed it, like it is now for the onside kick. I don't see this new rule changing the game or the strategy of the game at all.