Well its about time I wrote about my experiences with www.pbxnsip.com as a software based PBX and www.inphonex.com as an online SIP provider.
First off, I can't say enough about the support from pbxnsip so far! I was new to the VoIP world when I started investigating options for my lab environment where I wanted to build out something more than an IM and web conferencing solution. After working through many of the issues with my OCS Edge servers, I finally had an environment I could prove out all my scenarios and began looking for a software PBX.
Going back some time though, I had started with the "3CX" free PBX software as it seemed to have some ability to talk to things like Exchange 2007 Unified Messaging (even though you needed to buy a license to get it to work). My trouble soon began when I tried making outbound calls and realized 3CX couldn't handle e.164 phone numbers prefixed with a plus sign "+". I posted my concerns along with others on the forum and wasn't able to get much assistance other than a few pointed questions as to why we would want to implement OCS and digs on how Microsoft's SIP implementation is non-standard, etc. etc.
Somewhere along the way I found a post about pbxnsip and their work with Microsoft Office Communications Server. I quickly checked the compatibility guide for IP-PBX's and noticed they were already listed on the Exchange 2007 UM site: http://technet.microsoft.com/en-ca/library/cc164342.aspx#supIPPBX
So this was good news!
Even though they're not on the tekVizion list of certified PBX's for OCS --yet, this was a viable option. Thanks as well to their wiki page on the subject: http://wiki.pbxnsip.com/index.php/Office_Communications_Server.
So this is what I needed to get all the software bits in place, now it was time to find a SIP trunk provider. I asked around and did some digging online and found www.inphonex.com which I think is based in Miami, FL, USA. They were able to provide me a DID based in Edmonton, Alberta, Canada and their rates were decent. So far I've been happy with their service even though the odd time I call my DID I get a busy signal....but not to bad for a lab environment.
For those of you who are looking for an alternative to www.inphonex.com, check out www.voiphiway.ca as they seem to have slightly better prices and have a more "trusting" web presence.