I for one think it's a bad thing. Distractions and lack of focus are things that you should have to deal with. Here's my argument:It is the same concept as PED use in other sports, namely baseball. Players weren't hitting as many HR's (again, categorize HR's as a gradable part of how we grade those athletes) so they found an external source to artificially inflate their strength to boost their average hit distance (therefore more balls = HR). In both cases, instead of practicing to up that section of your game, you use something external to the sport to enhance it - whether it be drugs or equipment foreign to the competition is a moot point.
Secondly, this is unfair because you penalize those with good focus by giving those with less this handicap. What if Shaq had the choice of where to shoot his free throw from when he got fouled? He'd dunk them, and be the best FT shooter in the league, and it'd be a penalty to those who spend hours practicing a legitimate part of the sport and attribute of a players game. On top of all this, you have to remember professional = playing for money. Even though DG isn't much at this point, it will grow.
I wouldn't play poker for money against someone who was allowed to card count with a scratch pad next to him. Your abilities should stand on their own merits during competition. I know Climo has proven himself, and so has Des Reading, but I'm speaking more on the principle of allowing earbuds/music during competition. I'm NOT blasting them - there's no rule against it, they didn't do anything illegal - but there should be a rule is my stance. They are elite level players, they will be imitated.