Nice! Though, seems odd to me that each entry copies the original article but reformats the text poorly. Would it not be better to simply link to the article itself? As is, much of the code examples aren't formatted. Maybe I'm not understanding the purpose of this.
This is a fundamental problem with RSS/Atom based aggregation: people write their blog posts to work nicely with their own site's CSS, and then when the post is aggregated onto a different site with a different theme it can look very different. Some blogging engines try to avoid this by deliberately stripping out anything but basic HTML from the RSS version of a post, but that can create the same problem in the opposite direction.
In practice it's not a big deal, though. Most posts use pretty simple markup, and of the ones that don't, if you read a Planet regularly you learn pretty quickly whose posts are worth clicking through to the original site to read.
EDIT: As noted by Paul below, the site is back up.
It is a shame that the main elm-lang.org page is currently down. There are presumably a number of people like me that saw this submission and wanted to see what the language is like...
