I have never made a skype call, However I have had skype contacts call me, and it connects fine. They all connected from skype on Pc's, skype to skype.

As a caveat to that, all my skype usage is on wifi. Given the N900 takes ages connecting me to web 'n' walk (Minutes of time is wasted while it connects and longer to do anything online) I tend to use Wifi to browse and that might be a reason. By not going web'n'walk I am escaping the evil clutches of T-mobile and their IT services.

Hope that helps.