good voice quality with an sdk-based softphone

I started to use a free softphone (I don’t want to name it) for my business but it had poor voice quality and I got totally fed up with it, so I decided to change it for a better one. I tested then purchased Ozeki Voip sip sdk and the video and voice quality seems to be all right (s.p. for it: Addressing video qualiy). It supports many codecs and is compatible with lots of open source pbxes like Asterisk. Have you got similar experiences ? Any bad points?