As you might expect, I'm not a fan of the locked-hardware approach taken by most VoIP providers, especially since companies don't make it clear up front that retail VoIP boxes are locked to the specific provider. But maybe it's just me, since cell phone providers have been playing this game for years and this ploy doesn't seem to have affected their sales.
Despite my problems with the service, I like BroadVoice's BYOD for a number of reasons. First, it gives users freedom of choice in their VoIP hardware, which will become increasingly important as SIP-enabled devices become more diverse in features and configurations. Most VoIP service providers won't want to offer or support every device, and BYOD provides a greater freedom of choice for the consumer.
For the not-so-heavy caller such as myself, the BYOD "Lite" plan is just the ticket, providing both low cost and high flexibility. While Skype (plus SkypeOut and SkypeIn) costs about a buck a month less (assuming you use all 100 SkypeOut minutes a month), BYOD Lite provides more calling features and doesn't require a computer running to host the service.
Finally, BYOD expands options beyond the "small business" products currently offered by the mainstream retail VoIP providers. In some cases - BroadVoice included - these "business" plans differ only in their price and terms of service that officially allow the higher call volume expected from business use. BYOD opens up the ability for savvy businesses, or small VARs, to configure VoIP PBXs that more closely match the needs of "mom and pop" businesses that may only need a dozen or so phones per location.
The only fly in the VoIP hardware freedom-of-choice soup is the difficulty of finding unlocked hardware. But I'm sure that some helpful readers (and vendors) will post some comments to help you out in your quest for freedom of VoIP!