Shorter range, proprietary setup/configuration process, cycle IDs (crashing some android bluetooth stacks). They really want you to pay for the backend - wouldn't be surprised if they're sold at cost.
The batteries don't last as long as advertised either, but that's pretty much been true for all of the devices I've tested.
The batteries don't last as long as advertised either, but that's pretty much been true for all of the devices I've tested.