X-Lite, the only proprietary softphone of the bunch. Although it's not open source, it is free as in beer for personal or commercial use. Unlike the other softphones in this review, X-Lite is also available for Windows and Mac OS X.

The Linux version is provided as a tarball with the X-Lite binary. Just download, unzip, and run. X-Lite's Audio Tuning Wizard runs when you start it for the first time. This is a feature the other softphones should adopt.

It allows you to confirm that X-Lite is playing nice with your sound card and microphone. It even calibrates your microphone to adjust for the ambient noise level around the computer. These settings can be adjusted at any time by right-clicking the X-Lite client.

X-Lite's biggest strength is the usefulness of its interface. Without accessing any menus you can adjust the speaker volume, adjust the microphone volume, and choose which codecs are enabled. Another advantage is its three line appearances, one more than Twinkle supports. As far as features go, X-Lite has just about everything you can expect in a softphone.

Well, almost. While its interface is simple, its menu options are not. X-Lite has an overwhelming number of settings. For example, why have a menu option to disable codecs when they can be toggled on and off directly from the main interface? Another downside is that some of the features the other softphones offer, like Auto-Answer and Do Not Disturb, are locked.

I only found this out after trying to enable them with no luck. For those features to work, you must purchase X-Lite's successor, CounterPath's eyeBeam video and softphone. An audio-only version runs $30, and no Linux versions of eyeBeam are available at this time.