Instacast for Mac OS X has come out of beta and is available today as a trial or a US$14.99 purchase. The app is a versatile podcast manager and player that syncs with the iOS version of Instacast 3 ($4.99).
The Mac app mirrors the iOS version, allowing you to manage, delete, play and find audio or video podcasts of interest. The Mac app supports AirPlay, and podcasts can be shared via social networks or email. The Instacast system allows you to keep your podcasts in sync across all devices that have Instacast installed, and has some impressive search capabilities to help you if you don't know the name of the podcast you are looking for.
I tried the free demo version and found that it worked as expected. If you are a big podcast fan, this app and the related iOS system will be of value to you. If you are a more casual user, you can likely get by with Apple's solutions (iTunes for Mac and Podcasts for iOS), although they are more primitive than what Instacast offers. You might also want to look at Podsnatcher ($0.99) for Mac OS. It's not as full-featured as Instacast, but has some happy users writing reviews in the App Store.
Instacast is available direct from Vemedio for $5 off of the regular $19.99 price. The app requires OS X 10.8 or greater.