Pros: Enhance your stock iPod ear buds.
Cons: Difficult to attach and uncomfortable.
When I saw the bud fits I thought this was a great idea - my first mp3 player was a Rio Forge which came with sport ear buds that wraped around my ears in a similar manner to the bud fit extensions. We found the bud fits quite difficult to fit onto the iPod ear buds and when we did get them on (both my wife and I tried them) we found they were uncomfortable to wear. I think part of the issue for us is that we don't care for the stock iPhone ear buds in the first place so the BudFits only make a marginal improvement on the functionality of the base product. We tried the BudFits on other brands of ear buds we had in the house that we find more comfortable, but the product is really specifically designed for the Apple brand product. If a runner or athlete wanted an ear bud that stayed put I would get a purpose built set that is comfortable for their ears.