I have some CDs I want to trade/sell and will definitely be using Murfie.
I'm not sold on renting music I already own from them though. But then again I don't want to pay for online backup either, so I'm probably not the target market on that side of the business.
Of all those companies I think I worry more for Zoomshift than any of the others. Having worked in the restaurant business through middle and high school and part of college, every owner has slightly different rules around trading shifts, scheduling, etc.
Maybe they have a crazy customizable rules engine that owners can easily configure their own rules - that would be a killer feature. Without that I'm not sure they can break into many small-to-medium sized restaurants.
The other killer feature they could implement (if they don't already have it) is branding customized for each restaurant chain and/or owner. If your local restaurant that has 8 locations could get a customized version of Zoomshift for a reasonable monthly charge, had customizable rules and incredible support - that would be a no-brainer for most restaurant owners.
I'm not sold on renting music I already own from them though. But then again I don't want to pay for online backup either, so I'm probably not the target market on that side of the business.