Now, Slate has come to the iPhone in a US$1.99 app that features all the articles from the site, as well as the blog posts, staff tweets and streaming video from the Slate podcasts. Once content is downloaded you can read it off-line, which is a worthwhile feature. Access to Slate on the web is free, and you can read Slate from any mobile browser by going to mobile.slate.com.
So why the charge for the iPhone app? Slate says it cost something to develop it, and it gives you a much richer experience in a portable form. I can't argue with that, but I can argue with the ads that appear absolutely everywhere. Even the splash screen popped up with an ad. I think that's a bit much after I've paid for the app, but I'm beginning to see a lot of this in other apps as well.
I do like the app a lot, and it is a better experience for me than reading Slate stories in Safari on the iPhone. I even prefer the app to reading the site on my desktop or laptop. I just think the constant intrusive ads are a turn-off that will keep some people from pulling the trigger on what is an otherwise laudable effort.
Slate works on any iPhone or iPod touch with OS 3.0 or greater. I expect we'll see an iPad version as well.
Full disclosure: In the dim, distant past I worked at the Washington Post Company, which owns Slate.
Take a gander at some screen shots below: