Here are some notes that Marco included with the announcement:
Overcast 1.0 will be an iPhone app. I plan to get iPad support done relatively soon, but probably not for 1.0. I may never do a Mac app — that’s still up in the air, but definitely not for 1.0. And I have no plans to support Android — if you want an Android app, I hear Pocket Casts blows away everything else available, and they’re nice guys.
I have no plans to support video podcasts. That’s an entirely different medium with very different consumption habits, priorities, and needs. I can make a better app for audio podcasts by not supporting video at all.
I don’t plan to support streaming in 1.0, and may never add it. Overcast 1.0 will only play downloaded files. iOS 7’s background downloads, faster cellular networks, and larger-capacity phones have greatly reduced the need for streaming, and by not supporting it, I’m able to add some cool features and simplify a lot of the code and interface.
I give credit to Marco for determining what he thinks is the best solution for a podcasting app. Personally, I need a lot more from my podcasting applications than Marco is going to give initially,1 but Overcast might be a good fit for some people.
Relatedly, David Smith of Feed Wrangler just released a new podcatcher called Pod Wrangler which seems to have a similar approach to Overcast.2 If you are looking for a new podcatcher while Overcast is developed, it might be worth it to give Pod Wrangler a shot.3