yeah, i tend to agree with Chafe on this. I use mine for mowing the lawn however, because of the isolation my IEM's give.
Depends what sports you are doing. If it's walking, then you can use it np, but for active sports where a lump of this size and mass is jigging around, it's really down to how much it annoys you vs SQ tradeoffs. I use a Sansa Clip also for jogging, it's just so nice not to be distracted by the moving mass and also my Sennheiser ear buds are far nicer for this (no low frequency "bumping" that I get when jogging with the Grado GR10's).
In fact, this latter point is the biggest problem really, for sports; i can tolerate, or secure the mass, but the LF jolting is a real detraction and negates the boost in SQ. Perhaps with different IEM's i would go for the X3ii for active sports.
imho, go for the clip. Also, around 50 bucks is not going to break the bank if you drop it or damage it (and they are less likely to damage anyway if dropped) - and also for the buds, around 15 bucks for a half decent sound

. Obviously the more active you are, the more risk to your costly device and IEMs.