I think if you are getting sound feeding into your mic from your speakers (when on speakerphone) it happens with all apps. But for me personally, Skype let's out a somewhat quiet but annoying high pitch tone. Also, people more often than not say they can hear themselves echo back to them.
Whereas, phone calls, hangouts, etc. I am at least told by the other person about these issues less often. And I don't get the high pitch tone like I do in Skype.
In all cases, just plugging in headphones will fix the issue on all sides. Headphones with a mic or my bluetooth will also fix the issues.
