I've had extra on a few times this week at work, and it works quite well while grafting, tune after tune without hardly any annoying input apart from some adverts on a lot less than normal heart.
To be fair most songs are ones of the main playlist, but there are a lot more rarer tracks on that would normally only apear in time tunnel or all 80s, so certanly for work anyway not to bad for a hour or so a day.