I’ve been playing around with Gizmo the past couple of days. Gizmo is a free, P2P internet telephony product that is very similiar in many ways to the extremely popular Skype. However, unlike Skype, it is based on SIP, an open-standard for making internet phone calls, which means that Gizmo can make and receive calls from other internet phone networks. Which is a pretty big deal.

Gizmo’s not the first SIP client out there, but it’s extremely well designed, and appears to have little difficulty traversing firewalls and NAT routers, which is often a challenge for SIP-based products.

Like Skype, Gizmo offers end-to-end call encryption, the option to add cheap inbound and outbound calls to landlines, and has great sound quality.

Major plus over Skype: built-in call recording. This will be incredibly useful for podcasters and others who want to record high-quality interviews online.

Major downside compared to Skype: no built-in instant messaging. That’s a bummer, but I suspect it will be addressed soon, as folks are clamoring for it in the forums.

It’s nice to a see a credible competitor to Skype enter the market. Hopefully it will spur another round of rapid innovation.