or should you limit the characters and have a "read more" link

I go with the whole post. I also go with the full posts in RSS feeds as well. I am not against it and know it will generate more page views, but this is how I chose to do it.

I do read more. It looks better imo

From a design viewpoint, I would go with only displaying summaries if you have really long posts (over a few paragraphs). Then users who are selective can easily scroll and pick out some posts which they want to read instead of scrolling through pages without finding anything to read.

I go with shorter posts on the index page, but full articles in the RSS feed.

But considering that so few readers actually use the homepage -- they go straight to the article -- it doesn't really matter either way, unless you're looking for more page views.

In general I display the whole post but if its a really long article or something I know will get users to click the read more then sometimes I use that.