I have used this succesfully o communicate to a PC user and it worked fine. Exchanged a file with it too. No problem buying Skypeout credits it worked first time. Also speaking to a friend at work the other day we had a 20 min chat and he uses Skype for all his outgoing calls, that convinced me to give skypeout a go. However I have as suggested got out my old IBM viavoice microphone/headset Andrea Model NC7100 and apart from disappearing a few times (USB Hub issue?) it sounded Ok. However after purchasing some credits I tried a few outgoing calls. Called a friend and left a message and he could hardly hear it, also my son said the same on his mobile. so audio quality is an issue so far. Turned up the audio input to nearly maximum but it is hard to tell what the other end is hearing. Also when dialling out the ring tone seemed weird kind of doubled up and too fast.
One final thing I tried my Bluetooth headset Sony Ericsson HBH 35 and that works ok with the mac even listened to a podcast with it but not tried outgoing calls yet.