If you're competing against Cisco or other proprietary IP PBX solutions, some points of difference would be upfront cost, flexibility of using multiple vendors for acquisition and support (not locked in), and widely available compatible products (again, not locked in). On the other hand, Cisco users in my area tend to be centrally managed corporates, so you'd probably struggle to get a foot into that segment with PIAF. We've found our most likely PIAF-type customers have been small businesses that are looking to keep costs down. We also have our own SIP trunking service that we offer very good rates on, so that helps sell the overall PBX package. Some SIP providers have Dealer/Reseller facilities, so you can also make a couple of bucks off selling their trunks onto your PBXs. Customers tend to like having a single contact for their communications support, so don't dismiss the leverage of selling the trunks, too. Perhaps you can package it up with your IT sales and service for a fairly complete office solution.