I started using Skype when I moved 6,000 miles away from home. Talking from my laptop is cool, but I developed a real bad neck tension from instinctively moving my mouth closer to the microphone. Also when I'm in a cafe, where it's busy in the background and there's a bunch of strangers listening in, I can't really make the phone calls. So I decided I'd shop for a USB phone.
I stumbled upon the Free1 on a review of the Skype journal. The reviewer said this best-selling USB phone gave the user a full Skype experience, meaning better voice quality than a regular telephone. I also explored the wireless phones. I tried one, the linksys, but phone calls kept getting dropped. After reading reviews on cordless/wireless phones for Skype, I found out that Skype just doesn't support wireless, so you shouldn't waste $100 on them.
I got this phone and was truly amazed. It's true, when you make Skype to Skype phone, the voice quality is crystal clear, and much better than using a phone card on a regular telephone. The phone itself is wideband, which means it's 6 times clearer than a good'olde rotary phone. Better than my cellphone, too.
I ended up liking it so much I bought another one a few weeks ago for my sister, so that we, too, could talk for free (she's so cheap she doesn't even have a cell phone...). Love it! Easy to use, great voice quality.
Oh, and bonus: mac compatible.