I looked all over PhonePower's website, and decided against trying it. A lot of t he features I want are either not available, or cost extra. Incoming callerID name is not available. I believe the IVR capabilities cost extra. I don't remember what else, but I wasn't impressed, and thought Vestalink was a better deal.
That said, I think Anveo's normal non-obi approved plan is the one I like best, so far. I signed up for the $2/month unlimited incoming + $.80/month E911 service, no setup fees or commitment. So far, my $10 initial funding is mostly still there. :-) Their website is maddening to me, but I'm starting to get used to it. I think if I keep them, I'll set shortcuts for the pages I mostly use.
Anveo has good prices on outgoing calls, and with 6 second increments, a short call doesn't even cost a full penny. Canada is only .5 cents/minute, and China, which my wife calls is mostly 1.5 cents/minute, less that our calling card. Plus they have Fax in and out, no fax machine needed. You can upload fax bodies, fill out the header online, and incoming goes to email.