Did you guys that are opening it in IE think about opening it in Firefox? I just did in Firefox 2 and the posts are formated with [...] at the end.
The reason IE displays them differently is because if you view the source for the RSS feed, you will notice that full text of the post is there in between the <content:encoded></content:encoded> tags. Obviously, IE renders those.
If you use an aggregagtor such as Planet, this is an issue and should be resolved with either an option or a bug fix to put the full text in between the <description></description> tags.
If anyone has a solution other than to editing the RSS feed generation PHP code, please reply as I am looking for a solution as well.