OT: What vexes VoIP users?

[Eric Brunner-Williams <brunner () nic-naa net>]

OT, but NANOG is almost always good for quick clue ...

For those who have residential VoIP, what provider {features | bugs} 
are most vexing?

For those who provision residential VoIP, what subscriber 
{expectations | behaviors} are most vexing?

Thanks in advance,
Eric