If you're talking RSS feeds and regular readers, I still think it has to be full posts.
But when you're talking about a blog homepage, I think there's a subtle difference in the people likely to be visiting. They aren't so likely to be the tech savvy regular readers already grabbing your RSS reader, especially bearing in mind RSS really hasn't hit the main stream yet (even if you include the people using RSS who don't realise it).
I'd read that some people say their traffic goes up when they do that. Mine went down, but the number of Bloglines subscribers went up. They likely read the entire post at Bloglines, and never click into my blog. Now, if traffic contributes any hint of a positive to search results, this bothers me.
Not at all surprised there were less visits to the site, and more bloglines readers, and when you consider the other aggregators out there, is there a chance that your content is now actually being read by more people?
Which has the knock on effect of possible generating more links etc... to you....
I tend to subscribe to the Scoble point of view, that using full text RSS feeds is a way of connecting to influencers. Maybe not the people who would click on ads and stuff anyway, and who might not bother reading if there are full text feeds, but who are the kinds of people who might direct traffic to you if they are reading your content.
I think the only time those kinds of people are really going to be looking at blog home pages is when they first discover it, and want to check out other posts, or if they are coming back to find out more about who's behind a blog and other details about it.
Which is why I think a home page needs to be more scannable than the RSS feeds, shorter snippets of posts, along with the other stuff.