Linux Soft Phone Roundup
QuteCom

QuteCom Main Window
QuteCom is the only one of the soft phones I looked at that wasn't built using GTK+ or Gnome, rather it was built with Qt. I actually love Qt. I've written a whole lot of code using the Qt toolkit, including the soon to be released to the GPL TACC billing system. QuteCom is also quite a solid soft phone, but didn't quite pass my tests. The UI is about the only place where this app failed for me.
The use of tabs on the main window is off putting for me. It does have a quick box at the bottom for you to dial a number with. The window will just about double in width as soon as you make or receive a call, though.
It also supports video (though only V4L, not V4L2) and instant messaging accounts. It is undoubtedly one of the more polished soft phones that I have tried.
So why am I using SFLphone instead of QuteCom? The UI mostly. QuteCom has a very well thought out UI, but it still requires a lot of mouse clicks to do anything. It functions very well as a SIP phone, but then takes things further and tries to be an instant messaging client and address book and a video phone (which I was never able to get working). The lack of global hot keys was a pretty big factor for me.
QuteCom Conclusions
QuteCom deserves an honorable mention from me. Its a good soft phone, but in my opinion it tries to do a bit too much. I'm positive that there are a lot of people who would really like it, but for me it comes down to personal preference here and not functionality. QuteCom has most of the functionality, just not for me.
