When Marco Arment announced that he was making a podcast app, he was deliberately entering a crowded market. He said that he wanted to rid himself of his irrational fear of direct competition.
The crowded market doesn't seem to be hurting him. The reviews of his app Overcast in Macstories, Macworld, and elsewhere have all been great. But it's also important to note that the crowded market itself is not diluted by the number of independent developers entering it. On the contrary, the diversity of apps, and all the different approaches to the problem of podcast delivery, can serve to improve the quality of all those apps.
There's a post on the Supertop blog (the developers of the podcast app Castro) about why they welcome the competition from Overcast.
From our perspective, a user trying any third party app is good for all third party apps. If a user is persuaded to download one alternative they should be more likely to consider others in the future, especially given the variety of apps that are available...I encourage you to try Overcast. In fact, if you really love podcasts, I encourage you to try all the others too.
I have no background in design, but perhaps because I have a degree in comparative literature, I find it endlessly fascinating to compare the interface of apps and savor the details of what each one offers. None of these apps is perfect, but it's inspiring to see how a group of talented humans use their skills in different ways, through the endlessly plastic medium of software, to approach the same problems.