With a reasonably good net connection, the voice quality is great although the latency can be a bit much. I have it loaded on my laptop and I use a pair of cheapo ear buds and the laptop's built-in mike to call home when I'm in parts of the world where calling home is expensive, like Brazil or Morocco. I got a USB headset, but found that the sound quality with the earbuds is just as good and they take up a lot less space in my briefcase.
Little known but useful fact: Skype calls to toll-free numbers in the US and Canada are free, no Skypeout credit needed. I found that extremely handy one time when I was in New Zealand and I needed to change some US Airways plane tix for after I got back. The only number they publish is an 800 one, so I called it via Skype, from NZ, for free.
Not that I've ever seen. There's all sorts of "Skype phones" that are actually USB handsets or headsets that plug into your PC. There are some freestanding Skype phones, some of which are cordless phones with USB bases, some of which are wifi, a few of which are Bluetooth to your PC..
Um, your Skype phone rings. Normally only other Skype users can call you. For extra money, you can get a Skypein POTS number. A friend has one, to make it easier for people to find him when he's on the road, works OK, although I prefer my ordinary VoIP with voicemail-to-email.
R's, John