I work for Ringio (http://www.ringio.com http://www.ringio.com) so my advice is potentially subjective. Biggest differentiators: * You get a screen pop on your

I work for Ringio (http://www.ringio.com http://www.ringio.com) so my advice is potentially subjective. Biggest differentiators: * You get a screen pop on your computer (or your Android) when a call comes in, with the whole interaction history between the caller and anybody in your business, so your chances of sounding like you know what you're talking about are higher. * It syncs in real-time, 2 way, with your Google Contacts and makes it a snap to share contacts between colleagues. * It gives you fine-grained control over your Caller ID when making phone calls, so people who call you back are reaching you where they should (e.g. a support call shows your main company number, but a personal call shows your personal business number) * Unlike most of the other services, Making an outgoing call is not an afterthought, it's well built into the system as a full feature. And most startups trying to get customers do a lot of outbound calls, and rarely get called. (10:1 ratio)