No, but I've not done mnany calls yet. It sounds like the two endpoints of the Skype converstation might be "agreeing" on and using different encryption settings. Look to see if there's a pattern, like N900->Mac Skype v 72.1 bad, N900->N95 OK, and report it. Keeping a paper record is generally much more likely to spot this sort of thing.

I do find that the first few seconds of the call is frequently scratchy, but that it sorts itself out. This is N900->Win7 Skype 4.?, as a datapoint.