I'm a GNU/Linux user and therefore this article might be a bit jaded. I've completely given up on Skype for podcast interviews and have moved to Gizmo exclusively for the past few months. My main reason for making the initial move was the lack of recording functionality in Skype (which still doesn't exist), but now I find Gizmo to just be a superior product.
Gizmo is better than Skype because:
One button record. Need I say more?
Supports the SIP protocol which means that there are many, many ways to talk to VoIP users on other networks such as Google Talk and Astericks
The user interface is much cleaner and has tons of bells and whistles like a map you can bring up to see where the person you are talking to is from
Because of the SIP architecture, Gizmo can do things like ring several phones at once and transfer calls from your Gizmo client to your mobile phone in mid-call.
Free incoming telephone number in the 775 area code
Many more cool features that Skype just doesn't have